linux/drivers/char/Kconfig

597 lines
20 KiB

[PATCH] BLOCK: Make it possible to disable the block layer [try #6] Make it possible to disable the block layer. Not all embedded devices require it, some can make do with just JFFS2, NFS, ramfs, etc - none of which require the block layer to be present. This patch does the following: (*) Introduces CONFIG_BLOCK to disable the block layer, buffering and blockdev support. (*) Adds dependencies on CONFIG_BLOCK to any configuration item that controls an item that uses the block layer. This includes: (*) Block I/O tracing. (*) Disk partition code. (*) All filesystems that are block based, eg: Ext3, ReiserFS, ISOFS. (*) The SCSI layer. As far as I can tell, even SCSI chardevs use the block layer to do scheduling. Some drivers that use SCSI facilities - such as USB storage - end up disabled indirectly from this. (*) Various block-based device drivers, such as IDE and the old CDROM drivers. (*) MTD blockdev handling and FTL. (*) JFFS - which uses set_bdev_super(), something it could avoid doing by taking a leaf out of JFFS2's book. (*) Makes most of the contents of linux/blkdev.h, linux/buffer_head.h and linux/elevator.h contingent on CONFIG_BLOCK being set. sector_div() is, however, still used in places, and so is still available. (*) Also made contingent are the contents of linux/mpage.h, linux/genhd.h and parts of linux/fs.h. (*) Makes a number of files in fs/ contingent on CONFIG_BLOCK. (*) Makes mm/bounce.c (bounce buffering) contingent on CONFIG_BLOCK. (*) set_page_dirty() doesn't call __set_page_dirty_buffers() if CONFIG_BLOCK is not enabled. (*) fs/no-block.c is created to hold out-of-line stubs and things that are required when CONFIG_BLOCK is not set: (*) Default blockdev file operations (to give error ENODEV on opening). (*) Makes some /proc changes: (*) /proc/devices does not list any blockdevs. (*) /proc/diskstats and /proc/partitions are contingent on CONFIG_BLOCK. (*) Makes some compat ioctl handling contingent on CONFIG_BLOCK. (*) If CONFIG_BLOCK is not defined, makes sys_quotactl() return -ENODEV if given command other than Q_SYNC or if a special device is specified. (*) In init/do_mounts.c, no reference is made to the blockdev routines if CONFIG_BLOCK is not defined. This does not prohibit NFS roots or JFFS2. (*) The bdflush, ioprio_set and ioprio_get syscalls can now be absent (return error ENOSYS by way of cond_syscall if so). (*) The seclvl_bd_claim() and seclvl_bd_release() security calls do nothing if CONFIG_BLOCK is not set, since they can't then happen. Signed-Off-By: David Howells <dhowells@redhat.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
2006-09-30 20:45:40 +02:00
arch/tile: add hypervisor-based character driver for SPI flash ROM The first version of this patch proposed an arch/tile/drivers/ directory, but the consensus was that this was probably a poor choice for a place to group Tilera-specific drivers, and that in any case grouping by platform was discouraged, and grouping by function was preferred. This version of the patch addresses various issues raised in the community, primarily the absence of sysfs integration. The sysfs integration now handles passing information on sector size, page size, and total partition size to userspace as well. In addition, we now use a single "struct cdev" to manage all the partition minor devices, and dynamically discover the correct number of partitions from the hypervisor rather than using a module_param with a default value. This driver has no particular "peer" drivers it can be grouped with. It is sort of like an MTD driver for SPI ROM, but it doesn't group well with the other MTD devices since it relies on hypervisor virtualization to handle many of the irritating aspects of flash ROM management: sector awareness, background read for sub-sector writes, bit examination to determine whether a sector erase needs to be issued, etc. It is in fact more like an EEPROM driver, but the hypervisor virtualization does require a "flush" command if you wish to commit a sector write prior to writing to a different sector, and this is sufficiently different from generic I2C/SPI EEPROMs that as a result it doesn't group well with them either. The simple character device is already in use by a range of Tilera SPI ROM management tools, as well as by customers. In addition, using the simple character device actually simplifies the userspace tools, since they don't need to manage sector erase, background read, etc. This both simplifies the code (since we can uniformly manage plain files and the SPI ROM) as well as makes the user code portable to non-Linux platforms that don't offer the same MTD ioctls. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com> Reviewed-by: Arnd Bergmann <arnd@arndb.de>
2011-06-10 13:07:48 -04:00