On Fri, Nov 19, 2021 at 12:52 AM Guenter Roeck linux@roeck-us.net wrote:
On Fri, Nov 12, 2021 at 07:24:33PM +0800, Hsin-Yi Wang wrote:
edid_read() was assumed to return 0 on success. After 7f16d0f3b8e2("drm/bridge: anx7625: Propagate errors from sp_tx_rst_aux()"), the function can return >= 0 for successful case. Fix the g_edid_break condition in sp_tx_edid_read().
Fixes: 7f16d0f3b8e2("drm/bridge: anx7625: Propagate errors from sp_tx_rst_aux()") Signed-off-by: Hsin-Yi Wang hsinyi@chromium.org Reviewed-by: Robert Foss robert.foss@linaro.org
drivers/gpu/drm/bridge/analogix/anx7625.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c index 1a871f6b6822ee..392203b576042b 100644 --- a/drivers/gpu/drm/bridge/analogix/anx7625.c +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c @@ -826,7 +826,7 @@ static int sp_tx_edid_read(struct anx7625_data *ctx, g_edid_break = edid_read(ctx, offset, pblock_buf);
if (g_edid_break)
if (g_edid_break < 0) break;g_edid_break is declared u8 and thus never < 0. The break; statement doesn't indicate an error but that a break was encountered, and the value of g_edid_break == 1 is used elsewhere in the function to indicate that condition. It also doesn't break out of the outer loop, but only out of the switch statement.
With this patch in place, g_edid_break will have a more or less random value after an error, and the behavior of this function will be undefined.
Before 7f16d0f3b8e2("drm/bridge: anx7625: Propagate errors from sp_tx_rst_aux()"), edid_read() only returns 0 (i2c read bytes > 0) or -EIO, so g_edid_break also couldn't be 1. After checking the code more, I guess what it wants to do is:
- For the 1st and 2nd block (case 0 and 1) in sp_tx_edid_read(), copy the buffer on success. - For other blocks (case 2 and 3), process the buffer when the last g_edid_break updated in previous blocks is not 1. These blocks probably don't need to be updated if previous blocks have failed. The whole edid will be checked if valid.
I will update the patch.
Guenter