commit 74edd08a4fbf51d65fd8f4c7d8289cd0f392bd91 upstream.

When executing the following command, we met kernel dump.
dmesg -c > /dev/null; cd /sys;
for i in `ls /sys/kernel/debug/regmap/* -d`; do
	echo "Checking regmap in $i";
	cat $i/registers;
done && grep -ri "0x02d0" *;

It is because the count value is too big, and kmalloc fails. So add an
upper bound check to allow max size `PAGE_SIZE << (MAX_ORDER - 1)`.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Link: https://lore.kernel.org/r/1584064687-12964-1-git-send-email-peng.fan@nxp.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add support for dumping write only device registers in debugfs. This is
useful for audio codecs that have write only registers (like WM8731).
The logic that decides if a value can be printed is moved to
regmap_printable() function to allow for easier future updates.

Signed-off-by: Cristian Birsan <cristian.birsan@microchip.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

Unlike the registers file we don't have any substantial performance
concerns rendering the entire file (it involves no device accesses) so
just use seq_printf() to simplify the code.

Signed-off-by: Mark Brown <broonie@kernel.org>

By printing the newline character to entry, we can avoid accounting
for it manually in several places.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Mark Brown <broonie@kernel.org>

Since we know the length of entry and that there's room enough in the
output buffer, using memcpy instead of snprintf is simpler and
cheaper.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Mark Brown <broonie@kernel.org>

Calling strlen() no less than three times on entry is silly. Since
we're formatting into a buffer with plenty of room, there's no chance
of truncation, so snprintf() has actually returned the value we want,
meaning we don't even have to call strlen once.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Mark Brown <broonie@kernel.org>

Now we no longer use the scratch buffer for register length calculation
there is no need for callers to supply one.

Signed-off-by: Mark Brown <broonie@kernel.org>

The in kernel snprintf() will conveniently return the actual length of
the printed string even if not given an output beffer at all so just do
that rather than relying on the user to pass in a suitable buffer,
ensuring that we don't need to worry if the buffer was truncated due to
the size of the buffer passed in.

Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

If a read is attempted which is smaller than the line length then we may
underflow the subtraction we're doing with the unsigned size_t type so
move some of the calculation to be additions on the right hand side
instead in order to avoid this.

Reported-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

IS_ENABLED should only be used for CONFIG_* symbols.

I have done a small test:
  #define REGMAP_ALLOW_WRITE_DEBUGFS
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 0.

  #define REGMAP_ALLOW_WRITE_DEBUGFS 0
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 0.

  #define REGMAP_ALLOW_WRITE_DEBUGFS 1
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 1.

  #define REGMAP_ALLOW_WRITE_DEBUGFS 2
  IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) returns 0.

So fix the misuse of IS_ENABLED(REGMAP_ALLOW_WRITE_DEBUGFS) and switch to
use #if defined(REGMAP_ALLOW_WRITE_DEBUGFS) instead.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@kernel.org>