[PATCH AUTOSEL 6.16-5.4] i3c: add missing include to internal header

[Sasha Levin]

From: Wolfram Sang <wsa+renesas at sang-engineering.com>

[ Upstream commit 3b661ca549b9e5bb11d0bc97ada6110aac3282d2 ]

LKP found a random config which failed to build because IO accessors
were not defined:

   In file included from drivers/i3c/master.c:21:
   drivers/i3c/internals.h: In function 'i3c_writel_fifo':
>> drivers/i3c/internals.h:35:9: error: implicit declaration of function 'writesl' [-Werror=implicit-function-declaration]

Add the proper header to where the IO accessors are used.

Reported-by: kernel test robot <lkp at intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202507150208.BZDzzJ5E-lkp@intel.com/
Signed-off-by: Wolfram Sang <wsa+renesas at sang-engineering.com>
Reviewed-by: Frank Li <Frank.Li at nxp.com>
Link: https://lore.kernel.org/r/20250717120046.9022-2-wsa+renesas@sang-engineering.com
Signed-off-by: Alexandre Belloni <alexandre.belloni at bootlin.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
---

LLM Generated explanations, may be completely bogus:

**Backport Status: YES**

This commit should be backported to stable kernel trees for the
following reasons:

1. **Fixes a real build failure**: The commit fixes an actual
   compilation error where `writesl` function is used without including
   the proper header (`<linux/io.h>`). This is a concrete build
   regression that prevents kernel compilation in certain
   configurations.

2. **Minimal and safe change**: The fix is extremely simple - it only
   adds a single `#include <linux/io.h>` line to the internals.h header
   file. This is a one-line change with virtually no risk of introducing
   regressions.

3. **Detected by kernel test robot**: The issue was found by the Linux
   Kernel Test Robot (LKP), indicating it affects real-world build
   configurations that are tested regularly. The error message shows:
  ```
  drivers/i3c/internals.h:35:9: error: implicit declaration of function
  'writesl'
  ```

4. **Affects core I3C infrastructure**: The internals.h header is
   included by core I3C files (master.c and device.c), so a build
   failure here can prevent the entire I3C subsystem from compiling.

5. **Recent regression**: Looking at the git history, the
   `i3c_writel_fifo()` and `i3c_readl_fifo()` functions were recently
   added in commit 733b439375b4, and are already being used by I3C
   controller drivers (dw-i3c-master.c and cdns-i3c-master.c as shown in
   commits 6e055b1fb2fc and c20d3fa70491). This missing include is a
   regression that breaks builds after these recent changes.

6. **Clear stable backport criteria**: This meets the stable kernel
   rules perfectly:
   - It fixes a real bug (build failure)
   - It's obviously correct (missing include for used functions)
   - It's a minimal change (1 line)
   - No new features or architectural changes
   - Zero risk of functional regression

The commit is a textbook example of what should be backported to stable
trees - a simple, obvious fix for a build regression with no side
effects.

 drivers/i3c/internals.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/i3c/internals.h b/drivers/i3c/internals.h
index 433f6088b7ce..ce04aa4f269e 100644
--- a/drivers/i3c/internals.h
+++ b/drivers/i3c/internals.h
@@ -9,6 +9,7 @@
 #define I3C_INTERNALS_H
 
 #include <linux/i3c/master.h>
+#include <linux/io.h>
 
 void i3c_bus_normaluse_lock(struct i3c_bus *bus);
 void i3c_bus_normaluse_unlock(struct i3c_bus *bus);
-- 
2.39.5