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Hans de Goede 2766fae7c4 dma-mapping: Fix DMA_BIT_MASK() macro being broken 
commit 31b931bebd upstream.

After commit a50f7456f8 ("dma-mapping: Allow use of DMA_BIT_MASK(64) in
global scope"), the DMA_BIT_MASK() macro is broken when passed non trivial
statements for the value of 'n'. This is caused by the new version missing
parenthesis around 'n' when evaluating 'n'.

One example of this breakage is the IPU6 driver now crashing due to
it getting DMA-addresses with address bit 32 set even though it has
tried to set a 32 bit DMA mask.

The IPU6 CSI2 engine has a DMA mask of either 31 or 32 bits depending
on if it is in secure mode or not and it sets this masks like this:

        mmu_info->aperture_end =
                (dma_addr_t)DMA_BIT_MASK(isp->secure_mode ?
                                         IPU6_MMU_ADDR_BITS :
                                         IPU6_MMU_ADDR_BITS_NON_SECURE);

So the 'n' argument here is "isp->secure_mode ? IPU6_MMU_ADDR_BITS :
IPU6_MMU_ADDR_BITS_NON_SECURE" which gets expanded into:

isp->secure_mode ? IPU6_MMU_ADDR_BITS : IPU6_MMU_ADDR_BITS_NON_SECURE - 1

With the -1 only being applied in the non secure case, causing
the secure mode mask to be one 1 bit too large.

Fixes: a50f7456f8 ("dma-mapping: Allow use of DMA_BIT_MASK(64) in global scope")
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Link: https://lore.kernel.org/r/20251207184756.97904-1-johannes.goede@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2026-01-02 12:57:11 +01:00
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README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.