Re: [PATCH] drm/msm/dsi: add protection against NULL dsi device

[Abhinav Kumar <abhinavk@codeaurora.org>]

On 2019-05-29 13:43, Jeffrey Hugo wrote:
> On 3/7/2019 3:02 PM, Abhinav Kumar wrote:
>> On 2019-03-07 13:59, Sean Paul wrote:
>>> On Wed, Mar 06, 2019 at 05:28:54PM -0800, Abhinav Kumar wrote:
>>>> When panel probe happens after DSI probe, the DSI probe
>>>> is deferred as per current design. In the probe defer path
>>>> dsi device is destroyed. This NULL dsi device could be
>>>> deferenced by the panel probe in the mipi_dsi_attach path.
>>>> 
>>>> Check for NULL dsi device before accessing it.
>>> 
>>> It would be really nice to sort all of this out in a manner that's 
>>> not
>>> sprinkling NULL checks around the driver. I spent 5 minutes looking 
>>> around and
>>> couldn't really make sense of how all of these pieces interact, but 
>>> this seems
>>> like it might be an architectural problem (perhaps since dpu was 
>>> using its own
>>> panel stuff instead of drm_panel?).
>>> 
>>> Anyways, it'd be nice to fix that.
>>> 
>>> In the meantime, could you please add a big comment like the !dev 
>>> check in this
>>> function explaining how this situation can come to pass? That way the 
>>> knowledge
>>> isn't lost and whoever comes along to clean up all of these probe 
>>> checks will
>>> have some clue as to what's going on.
>>> 
>>> Sean
>> [Abhinav] Sure Sean, will add a detailed comment to explain the 
>> scenario
> 
> Abhinav, it looks like this may have dropped off your radar.  Do you
> know when you'll come back to it?
Hi Jeff, Yes i will upload a v2 with a detailed comment as sean 
requested within this week.
> 
>>> 
>>>> 
>>>> Reported-by: Jeffrey Hugo <jhugo@codeaurora.org>
>>>> Tested-by: Jeffrey Hugo <jhugo@codeaurora.org>
>>>> Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>
>>>> ---
>>>>  drivers/gpu/drm/msm/dsi/dsi_manager.c | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>> 
>>>> diff --git a/drivers/gpu/drm/msm/dsi/dsi_manager.c 
>>>> b/drivers/gpu/drm/msm/dsi/dsi_manager.c
>>>> index 80aa634..cc2569d 100644
>>>> --- a/drivers/gpu/drm/msm/dsi/dsi_manager.c
>>>> +++ b/drivers/gpu/drm/msm/dsi/dsi_manager.c
>>>> @@ -769,7 +769,7 @@ bool msm_dsi_manager_cmd_xfer_trigger(int id, 
>>>> u32 dma_base, u32 len)
>>>>  void msm_dsi_manager_attach_dsi_device(int id, u32 device_flags)
>>>>  {
>>>>      struct msm_dsi *msm_dsi = dsi_mgr_get_dsi(id);
>>>> -    struct drm_device *dev = msm_dsi->dev;
>>>> +    struct drm_device *dev = msm_dsi ? msm_dsi->dev : NULL;
>>>>      struct msm_drm_private *priv;
>>>>      struct msm_kms *kms;
>>>>      struct drm_encoder *encoder;
>>>> -- The Qualcomm Innovation Center, Inc. is a member of the Code 
>>>> Aurora Forum,
>>>> a Linux Foundation Collaborative Project
>>>> 
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