Messages in this thread Patch in this message | | | Subject | Re: [PATCH -V2] drm/sun4i: Grab reference of connector before return connector from sun4i_tcon_get_connector | From | He Ying <> | Date | Wed, 3 Nov 2021 10:26:42 +0800 |
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在 2021/11/2 23:03, Maxime Ripard 写道: > Hi, > > On Tue, Nov 02, 2021 at 04:46:28AM -0400, He Ying wrote: >> From the comments of drm_for_each_connector_iter(), we know >> that "connector is only valid within the list body, if you >> want to use connector after calling drm_connector_list_iter_end() >> then you need to grab your own reference first using >> drm_connector_get()". So fix the wrong use of connector >> according to the comments and then call drm_connector_put() >> after using connector finishes. >> >> Signed-off-by: He Ying <heying24@huawei.com> >> --- >> >> V2: >> Use proper subject prefix >> >> drivers/gpu/drm/sun4i/sun4i_tcon.c | 18 +++++++++++++----- >> 1 file changed, 13 insertions(+), 5 deletions(-) >> >> diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c >> index 9f06dec0fc61..24fa6784ee5f 100644 >> --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c >> +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c >> @@ -47,12 +47,12 @@ static struct drm_connector *sun4i_tcon_get_connector(const struct drm_encoder * >> drm_connector_list_iter_begin(encoder->dev, &iter); >> drm_for_each_connector_iter(connector, &iter) >> if (connector->encoder == encoder) { >> - drm_connector_list_iter_end(&iter); >> - return connector; >> + drm_connector_get(connector); >> + break; >> } >> drm_connector_list_iter_end(&iter); >> >> - return NULL; >> + return connector; > Connector might be uninitialized if we don't find one here
Connector should be NULL if we don't find one. The code is
#define drm_for_each_connector_iter(connector, iter) \ while ((connector = drm_connector_list_iter_next(iter)))
So, when we don't break from the while body, connector
can only be NULL.
> >> } >> >> static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder) >> @@ -65,6 +65,7 @@ static int sun4i_tcon_get_pixel_depth(const struct drm_encoder *encoder) >> return -EINVAL; >> >> info = &connector->display_info; >> + drm_connector_put(connector); >> if (info->num_bus_formats != 1) > We're still accessing connector->display_info here, but it might have been > freed already. Agree. I'll place it after using 'info' finishes in v3. > > Maxime
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