Re: [PATCH v3 03/14] drm/rockchip: analogix_dp: Apply drmm_encoder_init() instead of drm_simple_encoder_init()

[Damon Ding]

Hi Dmitry,

On 2025/7/26 8:12, Dmitry Baryshkov wrote:
> On Thu, Jul 24, 2025 at 04:02:53PM +0800, Damon Ding wrote:
> > Compared with drm_simple_encoder_init(), drmm_encoder_init() can handle
> > the cleanup automatically through registering drm_encoder_cleanup() with
> > drmm_add_action().
> >
> > Signed-off-by: Damon Ding <damon.ding@xxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/rockchip/analogix_dp-rockchip.c | 4 +---
> >   1 file changed, 1 insertion(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> > index d30f0983a53a..4ed6bf9e5377 100644
> > --- a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> > +++ b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
> > @@ -29,7 +29,6 @@
> >   #include <drm/drm_of.h>
> >   #include <drm/drm_panel.h>
> >   #include <drm/drm_probe_helper.h>
> > -#include <drm/drm_simple_kms_helper.h>
> >   
> >   #include "rockchip_drm_drv.h"
> >   
> > @@ -377,8 +376,7 @@ static int rockchip_dp_drm_create_encoder(struct rockchip_dp_device *dp)
> >   							     dev->of_node);
> >   	DRM_DEBUG_KMS("possible_crtcs = 0x%x\n", encoder->possible_crtcs);
> >   
> > -	ret = drm_simple_encoder_init(drm_dev, encoder,
> > -				      DRM_MODE_ENCODER_TMDS);
> > +	ret = drmm_encoder_init(drm_dev, encoder, NULL, DRM_MODE_ENCODER_TMDS, NULL);
>
> It's not possible to use drmm_encoder_init() here. Per the documentation
> the encoder data structure should be allocated by drmm_kzalloc().
> However this drm_encoder is a part of struct rockchip_dp_device. It's
> allocated by rockchip_dp_probe() via devm_kzalloc(). This means that it
> can potentially be freed before the drm device is completely released,
> creating a use-after-free error.
>
> >   	if (ret) {
> >   		DRM_ERROR("failed to initialize encoder with drm\n");
> >   		return ret;
> > --
> > 2.34.1

Got it. This patch will be dropped in the next version.

Best regards,
Damon