linux/drivers/mtd/mtdcore.c

2574 lines
66 KiB

mtd: merge mtdchar module with mtdcore The MTD subsystem has historically tried to be as configurable as possible. The side-effect of this is that its configuration menu is rather large, and we are gradually shrinking it. For example, we recently merged partitions support with the mtdcore. This patch does the next step - it merges the mtdchar module to mtdcore. And in this case this is not only about eliminating too fine-grained separation and simplifying the configuration menu. This is also about eliminating seemingly useless kernel module. Indeed, mtdchar is a module that allows user-space making use of MTD devices via /dev/mtd* character devices. If users do not enable it, they simply cannot use MTD devices at all. They cannot read or write the flash contents. Is it a sane and useful setup? I believe not. And everyone just enables mtdchar. Having mtdchar separate is also a little bit harmful. People sometimes miss the fact that they need to enable an additional configuration option to have user-space MTD interfaces, and then they wonder why on earth the kernel does not allow using the flash? They spend time asking around. Thus, let's just get rid of this module and make it part of mtd core. Note, mtdchar had additional configuration option to enable OTP interfaces, which are present on some flashes. I removed that option as well - it saves a really tiny amount space. [dwmw2: Strictly speaking, you can mount file systems on MTD devices just fine without the mtdchar (or mtdblock) devices; you just can't do other manipulations directly on the underlying device. But still I agree that it makes sense to make this unconditional. And Yay! we get to kill off an instance of checking CONFIG_foo_MODULE, which is an abomination that should never happen.] Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2013-03-14 13:27:40 +02:00
nvmem: add explicit config option to read old syntax fixed OF cells Binding for fixed NVMEM cells defined directly as NVMEM device subnodes has been deprecated. It has been replaced by the "fixed-layout" NVMEM layout binding. New syntax is meant to be clearer and should help avoiding imprecise bindings. NVMEM subsystem already supports the new binding. It should be a good idea to limit support for old syntax to existing drivers that actually support & use it (we can't break backward compatibility!). That way we additionally encourage new bindings & drivers to ignore deprecated binding. It wasn't clear (to me) if rtc and w1 code actually uses old syntax fixed cells. I enabled them to don't risk any breakage. Signed-off-by: Rafał Miłecki <rafal@milecki.pl> [for meson-{efuse,mx-efuse}.c] Acked-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> [for mtk-efuse.c, nvmem/core.c, nvmem-provider.h] Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> [MT8192, MT8195 Chromebooks] Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> [for microchip-otpc.c] Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com> [SAMA7G5-EK] Tested-by: Claudiu Beznea <claudiu.beznea@microchip.com> Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com> Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Link: https://lore.kernel.org/r/20231020105545.216052-3-srinivas.kandagatla@linaro.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-10-20 11:55:41 +01:00
mtd: core: Fix freeing of otp_info buffer Commit 4b361cfa8624 ("mtd: core: add OTP nvmem provider support") is causing the following panic ... ------------[ cut here ]------------ kernel BUG at /local/workdir/tegra/linux_next/kernel/mm/slab.c:2730! Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM Modules linked in: CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.13.0-rc2-next-20210518 #1 Hardware name: NVIDIA Tegra SoC (Flattened Device Tree) PC is at ___cache_free+0x3f8/0x51c ... [<c029bb1c>] (___cache_free) from [<c029c658>] (kfree+0xac/0x1bc) [<c029c658>] (kfree) from [<c06da094>] (mtd_otp_size+0xc4/0x108) [<c06da094>] (mtd_otp_size) from [<c06dc864>] (mtd_device_parse_register+0xe4/0x2b4) [<c06dc864>] (mtd_device_parse_register) from [<c06e3ccc>] (spi_nor_probe+0x210/0x2c0) [<c06e3ccc>] (spi_nor_probe) from [<c06e9578>] (spi_probe+0x88/0xac) [<c06e9578>] (spi_probe) from [<c066891c>] (really_probe+0x214/0x3a4) [<c066891c>] (really_probe) from [<c0668b14>] (driver_probe_device+0x68/0xc0) [<c0668b14>] (driver_probe_device) from [<c0666cf8>] (bus_for_each_drv+0x5c/0xbc) [<c0666cf8>] (bus_for_each_drv) from [<c0668694>] (__device_attach+0xe4/0x150) [<c0668694>] (__device_attach) from [<c06679e0>] (bus_probe_device+0x84/0x8c) [<c06679e0>] (bus_probe_device) from [<c06657f8>] (device_add+0x48c/0x868) [<c06657f8>] (device_add) from [<c06eb784>] (spi_add_device+0xa0/0x168) [<c06eb784>] (spi_add_device) from [<c06ec9a8>] (spi_register_controller+0x8b8/0xb38) [<c06ec9a8>] (spi_register_controller) from [<c06ecc3c>] (devm_spi_register_controller+0x14/0x50) [<c06ecc3c>] (devm_spi_register_controller) from [<c06f0510>] (tegra_spi_probe+0x33c/0x450) [<c06f0510>] (tegra_spi_probe) from [<c066abec>] (platform_probe+0x5c/0xb8) [<c066abec>] (platform_probe) from [<c066891c>] (really_probe+0x214/0x3a4) [<c066891c>] (really_probe) from [<c0668b14>] (driver_probe_device+0x68/0xc0) [<c0668b14>] (driver_probe_device) from [<c0668e30>] (device_driver_attach+0x58/0x60) [<c0668e30>] (device_driver_attach) from [<c0668eb8>] (__driver_attach+0x80/0xc8) [<c0668eb8>] (__driver_attach) from [<c0666c48>] (bus_for_each_dev+0x78/0xb8) [<c0666c48>] (bus_for_each_dev) from [<c0667c44>] (bus_add_driver+0x164/0x1e8) [<c0667c44>] (bus_add_driver) from [<c066997c>] (driver_register+0x7c/0x114) [<c066997c>] (driver_register) from [<c010223c>] (do_one_initcall+0x50/0x2b0) [<c010223c>] (do_one_initcall) from [<c11011f0>] (kernel_init_freeable+0x1a8/0x1fc) [<c11011f0>] (kernel_init_freeable) from [<c0c09190>] (kernel_init+0x8/0x118) [<c0c09190>] (kernel_init) from [<c01001b0>] (ret_from_fork+0x14/0x24) ... ---[ end trace 0f652dd222de75d7 ]--- In the function mtd_otp_size() a buffer is allocated by calling kmalloc() and a pointer to the buffer is stored in a variable 'info'. The pointer 'info' may then be incremented depending on the length returned from mtd_get_user/fact_prot_info(). If 'info' is incremented, when kfree() is called to free the buffer the above panic occurs because we are no longer passing the original address of the buffer allocated. Fix this by indexing through the buffer allocated to avoid incrementing the pointer. Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support") Signed-off-by: Jon Hunter <jonathanh@nvidia.com> Reviewed-by: Michael Walle <michael@walle.cc> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Link: https://lore.kernel.org/linux-mtd/20210518185503.162787-1-jonathanh@nvidia.com
2021-05-18 19:55:03 +01:00
mtd: limit OTP NVMEM cell parse to non-NAND devices MTD OTP logic is very fragile on parsing NVMEM cell and can be problematic with some specific kind of devices. The problem was discovered by e87161321a40 ("mtd: rawnand: macronix: OTP access for MX30LFxG18AC") where OTP support was added to a NAND device. With the case of NAND devices, it does require a node where ECC info are declared and all the fixed partitions, and this cause the OTP codepath to parse this node as OTP NVMEM cells, making probe fail and the NAND device registration fail. MTD OTP parsing should have been limited to always using compatible to prevent this error by using node with compatible "otp-user" or "otp-factory". NVMEM across the years had various iteration on how cells could be declared in DT, in some old implementation, no_of_node should have been enabled but now add_legacy_fixed_of_cells should be used to disable NVMEM to parse child node as NVMEM cell. To fix this and limit any regression with other MTD that makes use of declaring OTP as direct child of the dev node, disable add_legacy_fixed_of_cells if we detect the MTD type is Nand. With the following logic, the OTP NVMEM entry is correctly created with no cells and the MTD Nand is correctly probed and partitions are correctly exposed. Fixes: 4b361cfa8624 ("mtd: core: add OTP nvmem provider support") Cc: <stable@vger.kernel.org> # v6.7+ Signed-off-by: Christian Marangi <ansuelsmth@gmail.com> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com> Link: https://lore.kernel.org/linux-mtd/20240412105030.1598-1-ansuelsmth@gmail.com
2024-04-12 12:50:26 +02:00
mtd: don't WARN about overloaded users of mtd->reboot_notifier.notifier_call There are multiple types of users of mtd->reboot_notifier.notifier_call: (1) A while back, the cfi_cmdset_000{1,2} chip drivers implemented a reboot notifier to (on a best effort basis) attempt to reset their flash chips before rebooting. (2) More recently, we implemented a common _reboot() hook so that MTD drivers (particularly, NAND flash) could better halt I/O operations without having to reimplement the same notifier boilerplate. Currently, the WARN_ONCE() condition here was written to handle (2), but at the same time it mis-diagnosed case (1) as an already-registered MTD. Let's fix this by having the WARN_ONCE() condition better imitate the condition that immediately follows it. (Wow, I don't know how I missed that one.) (Side note: Unfortunately, we can't yet combine the reboot notifier code for (1) and (2) with a patch like [1], because some users of (1) also use mtdconcat, and so the mtd_info struct from cfi_cmdset_000{1,2} won't actually get registered with mtdcore, and therefore their reboot notifier won't get registered.) [1] http://patchwork.ozlabs.org/patch/417981/ Suggested-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Brian Norris <computersforpeace@gmail.com> Cc: Jesper Nilsson <jespern@axis.com> Cc: linux-cris-kernel@axis.com Tested-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar> Tested-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Brian Norris <computersforpeace@gmail.com>
2015-11-03 17:01:53 -08:00
mtd: Fix the behavior of OTP write if there is not enough room for data If a write to one time programmable memory (OTP) hits the end of this memory area, no more data can be written. The count variable in mtdchar_write() in drivers/mtd/mtdchar.c is not decreased anymore. We are trapped in the loop forever, mtdchar_write() will never return in this case. The desired behavior of a write in such a case is described in [1]: - Try to write as much data as possible, truncate the write to fit into the available memory and return the number of bytes that actually have been written. - If no data could be written at all, return -ENOSPC. This patch fixes the behavior of OTP write if there is not enough space for all data: 1) mtd_write_user_prot_reg() in drivers/mtd/mtdcore.c is modified to return -ENOSPC if no data could be written at all. 2) mtdchar_write() is modified to handle -ENOSPC correctly. Exit if a write returned -ENOSPC and yield the correct return value, either then number of bytes that could be written, or -ENOSPC, if no data could be written at all. Furthermore the patch harmonizes the behavior of the OTP memory write in drivers/mtd/devices/mtd_dataflash.c with the other implementations and the requirements from [1]. Instead of returning -EINVAL if the data does not fit into the OTP memory, we try to write as much data as possible/truncate the write. [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html Signed-off-by: Christian Riesch <christian.riesch@omicron.at> Signed-off-by: Brian Norris <computersforpeace@gmail.com>
2014-03-06 12:42:37 +01:00
mtd: Fix the behavior of OTP write if there is not enough room for data If a write to one time programmable memory (OTP) hits the end of this memory area, no more data can be written. The count variable in mtdchar_write() in drivers/mtd/mtdchar.c is not decreased anymore. We are trapped in the loop forever, mtdchar_write() will never return in this case. The desired behavior of a write in such a case is described in [1]: - Try to write as much data as possible, truncate the write to fit into the available memory and return the number of bytes that actually have been written. - If no data could be written at all, return -ENOSPC. This patch fixes the behavior of OTP write if there is not enough space for all data: 1) mtd_write_user_prot_reg() in drivers/mtd/mtdcore.c is modified to return -ENOSPC if no data could be written at all. 2) mtdchar_write() is modified to handle -ENOSPC correctly. Exit if a write returned -ENOSPC and yield the correct return value, either then number of bytes that could be written, or -ENOSPC, if no data could be written at all. Furthermore the patch harmonizes the behavior of the OTP memory write in drivers/mtd/devices/mtd_dataflash.c with the other implementations and the requirements from [1]. Instead of returning -EINVAL if the data does not fit into the OTP memory, we try to write as much data as possible/truncate the write. [1] http://pubs.opengroup.org/onlinepubs/9699919799/functions/write.html Signed-off-by: Christian Riesch <christian.riesch@omicron.at> Signed-off-by: Brian Norris <computersforpeace@gmail.com>
2014-03-06 12:42:37 +01:00
mtd: create function to perform large allocations Introduce a common function to handle large, contiguous kmalloc buffer allocations by exponentially backing off on the size of the requested kernel transfer buffer until it succeeds or until the requested transfer buffer size falls below the page size. This helps ensure the operation can succeed under low-memory, highly- fragmented situations albeit somewhat more slowly. Artem: so this patch solves the problem that the kernel tries to kmalloc too large buffers, which (a) may fail and does fail - people complain about this, and (b) slows down the system in case of high memory fragmentation, because the kernel starts dropping caches, writing back, swapping, etc. But we do not really have to allocate a lot of memory to do the I/O, we may do this even with as little as one min. I/O unit (NAND page) of RAM. So the idea of this patch is that if the user asks to read or write a lot, we try to kmalloc a lot, with GFP flags which make the kernel _not_ drop caches, etc. If we can allocate it - good, if not - we try to allocate twice as less, and so on, until we reach the min. I/O unit size, which is our last resort allocation and use the normal GFP_KERNEL flag. Artem: re-write the allocation function so that it makes sure the allocated buffer is aligned to the min. I/O size of the flash. Signed-off-by: Grant Erickson <marathon96@gmail.com> Tested-by: Ben Gardiner <bengardiner@nanometrics.ca> Tested-by: Stefano Babic <sbabic@denx.de> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2011-04-08 08:51:32 -07:00
mtd: create function to perform large allocations Introduce a common function to handle large, contiguous kmalloc buffer allocations by exponentially backing off on the size of the requested kernel transfer buffer until it succeeds or until the requested transfer buffer size falls below the page size. This helps ensure the operation can succeed under low-memory, highly- fragmented situations albeit somewhat more slowly. Artem: so this patch solves the problem that the kernel tries to kmalloc too large buffers, which (a) may fail and does fail - people complain about this, and (b) slows down the system in case of high memory fragmentation, because the kernel starts dropping caches, writing back, swapping, etc. But we do not really have to allocate a lot of memory to do the I/O, we may do this even with as little as one min. I/O unit (NAND page) of RAM. So the idea of this patch is that if the user asks to read or write a lot, we try to kmalloc a lot, with GFP flags which make the kernel _not_ drop caches, etc. If we can allocate it - good, if not - we try to allocate twice as less, and so on, until we reach the min. I/O unit size, which is our last resort allocation and use the normal GFP_KERNEL flag. Artem: re-write the allocation function so that it makes sure the allocated buffer is aligned to the min. I/O size of the flash. Signed-off-by: Grant Erickson <marathon96@gmail.com> Tested-by: Ben Gardiner <bengardiner@nanometrics.ca> Tested-by: Stefano Babic <sbabic@denx.de> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2011-04-08 08:51:32 -07:00
mtd: create function to perform large allocations Introduce a common function to handle large, contiguous kmalloc buffer allocations by exponentially backing off on the size of the requested kernel transfer buffer until it succeeds or until the requested transfer buffer size falls below the page size. This helps ensure the operation can succeed under low-memory, highly- fragmented situations albeit somewhat more slowly. Artem: so this patch solves the problem that the kernel tries to kmalloc too large buffers, which (a) may fail and does fail - people complain about this, and (b) slows down the system in case of high memory fragmentation, because the kernel starts dropping caches, writing back, swapping, etc. But we do not really have to allocate a lot of memory to do the I/O, we may do this even with as little as one min. I/O unit (NAND page) of RAM. So the idea of this patch is that if the user asks to read or write a lot, we try to kmalloc a lot, with GFP flags which make the kernel _not_ drop caches, etc. If we can allocate it - good, if not - we try to allocate twice as less, and so on, until we reach the min. I/O unit size, which is our last resort allocation and use the normal GFP_KERNEL flag. Artem: re-write the allocation function so that it makes sure the allocated buffer is aligned to the min. I/O size of the flash. Signed-off-by: Grant Erickson <marathon96@gmail.com> Tested-by: Ben Gardiner <bengardiner@nanometrics.ca> Tested-by: Stefano Babic <sbabic@denx.de> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2011-04-08 08:51:32 -07:00
mm, page_alloc: distinguish between being unable to sleep, unwilling to sleep and avoiding waking kswapd __GFP_WAIT has been used to identify atomic context in callers that hold spinlocks or are in interrupts. They are expected to be high priority and have access one of two watermarks lower than "min" which can be referred to as the "atomic reserve". __GFP_HIGH users get access to the first lower watermark and can be called the "high priority reserve". Over time, callers had a requirement to not block when fallback options were available. Some have abused __GFP_WAIT leading to a situation where an optimisitic allocation with a fallback option can access atomic reserves. This patch uses __GFP_ATOMIC to identify callers that are truely atomic, cannot sleep and have no alternative. High priority users continue to use __GFP_HIGH. __GFP_DIRECT_RECLAIM identifies callers that can sleep and are willing to enter direct reclaim. __GFP_KSWAPD_RECLAIM to identify callers that want to wake kswapd for background reclaim. __GFP_WAIT is redefined as a caller that is willing to enter direct reclaim and wake kswapd for background reclaim. This patch then converts a number of sites o __GFP_ATOMIC is used by callers that are high priority and have memory pools for those requests. GFP_ATOMIC uses this flag. o Callers that have a limited mempool to guarantee forward progress clear __GFP_DIRECT_RECLAIM but keep __GFP_KSWAPD_RECLAIM. bio allocations fall into this category where kswapd will still be woken but atomic reserves are not used as there is a one-entry mempool to guarantee progress. o Callers that are checking if they are non-blocking should use the helper gfpflags_allow_blocking() where possible. This is because checking for __GFP_WAIT as was done historically now can trigger false positives. Some exceptions like dm-crypt.c exist where the code intent is clearer if __GFP_DIRECT_RECLAIM is used instead of the helper due to flag manipulations. o Callers that built their own GFP flags instead of starting with GFP_KERNEL and friends now also need to specify __GFP_KSWAPD_RECLAIM. The first key hazard to watch out for is callers that removed __GFP_WAIT and was depending on access to atomic reserves for inconspicuous reasons. In some cases it may be appropriate for them to use __GFP_HIGH. The second key hazard is callers that assembled their own combination of GFP flags instead of starting with something like GFP_KERNEL. They may now wish to specify __GFP_KSWAPD_RECLAIM. It's almost certainly harmless if it's missed in most cases as other activity will wake kswapd. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2015-11-06 16:28:21 -08:00
mtd: create function to perform large allocations Introduce a common function to handle large, contiguous kmalloc buffer allocations by exponentially backing off on the size of the requested kernel transfer buffer until it succeeds or until the requested transfer buffer size falls below the page size. This helps ensure the operation can succeed under low-memory, highly- fragmented situations albeit somewhat more slowly. Artem: so this patch solves the problem that the kernel tries to kmalloc too large buffers, which (a) may fail and does fail - people complain about this, and (b) slows down the system in case of high memory fragmentation, because the kernel starts dropping caches, writing back, swapping, etc. But we do not really have to allocate a lot of memory to do the I/O, we may do this even with as little as one min. I/O unit (NAND page) of RAM. So the idea of this patch is that if the user asks to read or write a lot, we try to kmalloc a lot, with GFP flags which make the kernel _not_ drop caches, etc. If we can allocate it - good, if not - we try to allocate twice as less, and so on, until we reach the min. I/O unit size, which is our last resort allocation and use the normal GFP_KERNEL flag. Artem: re-write the allocation function so that it makes sure the allocated buffer is aligned to the min. I/O size of the flash. Signed-off-by: Grant Erickson <marathon96@gmail.com> Tested-by: Ben Gardiner <bengardiner@nanometrics.ca> Tested-by: Stefano Babic <sbabic@denx.de> Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2011-04-08 08:51:32 -07:00
mtd: merge mtdchar module with mtdcore The MTD subsystem has historically tried to be as configurable as possible. The side-effect of this is that its configuration menu is rather large, and we are gradually shrinking it. For example, we recently merged partitions support with the mtdcore. This patch does the next step - it merges the mtdchar module to mtdcore. And in this case this is not only about eliminating too fine-grained separation and simplifying the configuration menu. This is also about eliminating seemingly useless kernel module. Indeed, mtdchar is a module that allows user-space making use of MTD devices via /dev/mtd* character devices. If users do not enable it, they simply cannot use MTD devices at all. They cannot read or write the flash contents. Is it a sane and useful setup? I believe not. And everyone just enables mtdchar. Having mtdchar separate is also a little bit harmful. People sometimes miss the fact that they need to enable an additional configuration option to have user-space MTD interfaces, and then they wonder why on earth the kernel does not allow using the flash? They spend time asking around. Thus, let's just get rid of this module and make it part of mtd core. Note, mtdchar had additional configuration option to enable OTP interfaces, which are present on some flashes. I removed that option as well - it saves a really tiny amount space. [dwmw2: Strictly speaking, you can mount file systems on MTD devices just fine without the mtdchar (or mtdblock) devices; you just can't do other manipulations directly on the underlying device. But still I agree that it makes sense to make this unconditional. And Yay! we get to kill off an instance of checking CONFIG_foo_MODULE, which is an abomination that should never happen.] Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2013-03-14 13:27:40 +02:00
mtd: merge mtdchar module with mtdcore The MTD subsystem has historically tried to be as configurable as possible. The side-effect of this is that its configuration menu is rather large, and we are gradually shrinking it. For example, we recently merged partitions support with the mtdcore. This patch does the next step - it merges the mtdchar module to mtdcore. And in this case this is not only about eliminating too fine-grained separation and simplifying the configuration menu. This is also about eliminating seemingly useless kernel module. Indeed, mtdchar is a module that allows user-space making use of MTD devices via /dev/mtd* character devices. If users do not enable it, they simply cannot use MTD devices at all. They cannot read or write the flash contents. Is it a sane and useful setup? I believe not. And everyone just enables mtdchar. Having mtdchar separate is also a little bit harmful. People sometimes miss the fact that they need to enable an additional configuration option to have user-space MTD interfaces, and then they wonder why on earth the kernel does not allow using the flash? They spend time asking around. Thus, let's just get rid of this module and make it part of mtd core. Note, mtdchar had additional configuration option to enable OTP interfaces, which are present on some flashes. I removed that option as well - it saves a really tiny amount space. [dwmw2: Strictly speaking, you can mount file systems on MTD devices just fine without the mtdchar (or mtdblock) devices; you just can't do other manipulations directly on the underlying device. But still I agree that it makes sense to make this unconditional. And Yay! we get to kill off an instance of checking CONFIG_foo_MODULE, which is an abomination that should never happen.] Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2013-03-14 13:27:40 +02:00
mtd: merge mtdchar module with mtdcore The MTD subsystem has historically tried to be as configurable as possible. The side-effect of this is that its configuration menu is rather large, and we are gradually shrinking it. For example, we recently merged partitions support with the mtdcore. This patch does the next step - it merges the mtdchar module to mtdcore. And in this case this is not only about eliminating too fine-grained separation and simplifying the configuration menu. This is also about eliminating seemingly useless kernel module. Indeed, mtdchar is a module that allows user-space making use of MTD devices via /dev/mtd* character devices. If users do not enable it, they simply cannot use MTD devices at all. They cannot read or write the flash contents. Is it a sane and useful setup? I believe not. And everyone just enables mtdchar. Having mtdchar separate is also a little bit harmful. People sometimes miss the fact that they need to enable an additional configuration option to have user-space MTD interfaces, and then they wonder why on earth the kernel does not allow using the flash? They spend time asking around. Thus, let's just get rid of this module and make it part of mtd core. Note, mtdchar had additional configuration option to enable OTP interfaces, which are present on some flashes. I removed that option as well - it saves a really tiny amount space. [dwmw2: Strictly speaking, you can mount file systems on MTD devices just fine without the mtdchar (or mtdblock) devices; you just can't do other manipulations directly on the underlying device. But still I agree that it makes sense to make this unconditional. And Yay! we get to kill off an instance of checking CONFIG_foo_MODULE, which is an abomination that should never happen.] Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
2013-03-14 13:27:40 +02:00