Hi Dan Carpenter,
>
>-----Original Message-----
>From: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
>Sent: Wednesday, January 8, 2025 5:14 PM
>To: Hermes Wu (吳佳宏) <Hermes.Wu@xxxxxxxxxx>
>Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
>Subject: [bug report] drm/bridge: it6505: fix HDCP CTS compare V matching
>
>Hello Hermes Wu,
>
>Commit 0989c02c7a5c ("drm/bridge: it6505: fix HDCP CTS compare V
>matching") from Dec 30, 2024 (linux-next), leads to the following Smatch static checker warning:
>
> drivers/gpu/drm/bridge/ite-it6505.c:2253 it6505_hdcp_part2_ksvlist_check()
> warn: ignoring unreachable code.
>
>drivers/gpu/drm/bridge/ite-it6505.c
> 2230 static bool it6505_hdcp_part2_ksvlist_check(struct it6505 *it6505)
> 2231 {
> 2232 struct device *dev = it6505->dev;
> 2233 u8 av[5][4], bv[5][4];
> 2234 int i, err, retry;
> 2235
> 2236 i = it6505_setup_sha1_input(it6505, it6505->sha1_input);
> 2237 if (i <= 0) {
> 2238 dev_err(dev, "SHA-1 Input length error %d", i);
> 2239 return false;
> 2240 }
> 2241
> 2242 it6505_sha1_digest(it6505, it6505->sha1_input, i, (u8 *)av);
> 2243 /*1B-05 V' must retry 3 times */
> 2244 for (retry = 0; retry < 3; retry++) {
> 2245 err = it6505_get_dpcd(it6505, DP_AUX_HDCP_V_PRIME(0), (u8 *)bv,
> 2246 sizeof(bv));
> 2247
> 2248 if (err < 0) {
> 2249 dev_err(dev, "Read V' value Fail %d", retry);
> 2250 continue;
> 2251 }
> 2252
>--> 2253 for (i = 0; i < 5; i++) {
>
>This looks like a loop from 0-4.
>
> 2254 if (bv[i][3] != av[i][0] || bv[i][2] != av[i][1] ||
> 2255 av[i][1] != av[i][2] || bv[i][0] != av[i][3])
> 2256 break;
> 2257
> 2258 DRM_DEV_DEBUG_DRIVER(dev, "V' all match!! %d, %d", retry, i);
> 2259 return true;
>
>But it is a "loop" from 0-0.
I have fix this in following,
https://lore.kernel.org/all/20250108-fix-hdcp-v-comp-v1-1-9404811825cd@xxxxxxxxxx/
Thanks a lot.
> 2260 }
> 2261 }
> 2262
> 2263 DRM_DEV_DEBUG_DRIVER(dev, "V' NOT match!! %d", retry);
> 2264 return false;
> 2265 }
>
>regards,
>dan carpenter
>
BR,
Hermes
