From: Arnd Bergmann <a...@arndb.de>

gcc warns about an sprintf() that uses the same buffer as source
and destination, which is undefined behavior in C99:

drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c: In function 
'amdgpu_securedisplay_debugfs_write':
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:141:6: error: 'sprintf' 
argument 3 overlaps destination object 'i2c_output' [-Werror=restrict]
  141 |      sprintf(i2c_output, "%s 0x%X", i2c_output,
      |      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  142 |       
securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
      |       
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c:97:7: note: destination 
object referenced by 'restrict'-qualified argument 1 was declared here
   97 |  char i2c_output[256];
      |       ^~~~~~~~~~

Rewrite it to remember the current offset into the buffer instead.

Signed-off-by: Arnd Bergmann <a...@arndb.de>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
index 834440ab9ff7..69d7f6bff5d4 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
@@ -136,9 +136,10 @@ static ssize_t amdgpu_securedisplay_debugfs_write(struct 
file *f, const char __u
                ret = psp_securedisplay_invoke(psp, 
TA_SECUREDISPLAY_COMMAND__SEND_ROI_CRC);
                if (!ret) {
                        if (securedisplay_cmd->status == 
TA_SECUREDISPLAY_STATUS__SUCCESS) {
+                               int pos = 0;
                                memset(i2c_output,  0, sizeof(i2c_output));
                                for (i = 0; i < 
TA_SECUREDISPLAY_I2C_BUFFER_SIZE; i++)
-                                       sprintf(i2c_output, "%s 0x%X", 
i2c_output,
+                                       pos += sprintf(i2c_output + pos, " 
0x%X",
                                                
securedisplay_cmd->securedisplay_out_message.send_roi_crc.i2c_buf[i]);
                                dev_info(adev->dev, "SECUREDISPLAY: I2C buffer 
out put is :%s\n", i2c_output);
                        } else {
-- 
2.29.2

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