amdgpu: fix gcc -Wrestrict warning

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 <arnd@arndb.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
index 9cf856c..1e59901 100644 (file)
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_securedisplay.c
@@ -139,9 +139,10 @@ 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 {