[RESEND 3/3] drm/amd/display: switch to guid_gen() to generate valid GUIDs

[Daniel Vetter]

On Mon, Aug 12, 2024 at 03:23:12PM +0300, Jani Nikula wrote:
> Instead of just smashing jiffies into a GUID, use guid_gen() to generate
> RFC 4122 compliant GUIDs.
> 
> Signed-off-by: Jani Nikula <jani.nikula at intel.com>
> 
> ---
> 
> Side note, it baffles me why amdgpu has a copy of this instead of
> plumbing it into drm mst code.

Yeah ec5fa9fcdeca ("drm/amd/display: Adjust the MST resume flow") promised
a follow-up, but that seems to have never materialized. Really should
materialize though. Patch lgtm

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>


> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 23 ++++++++++---------
>  1 file changed, 12 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 72c10fc2c890..ce05e7e2a383 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -2568,9 +2568,9 @@ static int dm_late_init(void *handle)
>  
>  static void resume_mst_branch_status(struct drm_dp_mst_topology_mgr *mgr)
>  {
> +	u8 buf[UUID_SIZE];
> +	guid_t guid;
>  	int ret;
> -	u8 guid[16];
> -	u64 tmp64;
>  
>  	mutex_lock(&mgr->lock);
>  	if (!mgr->mst_primary)
> @@ -2591,26 +2591,27 @@ static void resume_mst_branch_status(struct drm_dp_mst_topology_mgr *mgr)
>  	}
>  
>  	/* Some hubs forget their guids after they resume */
> -	ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, guid, 16);
> -	if (ret != 16) {
> +	ret = drm_dp_dpcd_read(mgr->aux, DP_GUID, buf, sizeof(buf));
> +	if (ret != sizeof(buf)) {
>  		drm_dbg_kms(mgr->dev, "dpcd read failed - undocked during suspend?\n");
>  		goto out_fail;
>  	}
>  
> -	if (memchr_inv(guid, 0, 16) == NULL) {
> -		tmp64 = get_jiffies_64();
> -		memcpy(&guid[0], &tmp64, sizeof(u64));
> -		memcpy(&guid[8], &tmp64, sizeof(u64));
> +	import_guid(&guid, buf);
>  
> -		ret = drm_dp_dpcd_write(mgr->aux, DP_GUID, guid, 16);
> +	if (guid_is_null(&guid)) {
> +		guid_gen(&guid);
> +		export_guid(buf, &guid);
>  
> -		if (ret != 16) {
> +		ret = drm_dp_dpcd_write(mgr->aux, DP_GUID, buf, sizeof(buf));
> +
> +		if (ret != sizeof(buf)) {
>  			drm_dbg_kms(mgr->dev, "check mstb guid failed - undocked during suspend?\n");
>  			goto out_fail;
>  		}
>  	}
>  
> -	import_guid(&mgr->mst_primary->guid, guid);
> +	guid_copy(&mgr->mst_primary->guid, &guid);
>  
>  out_fail:
>  	mutex_unlock(&mgr->lock);
> -- 
> 2.39.2
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch