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SubjectRe: [PATCH] drm/bridge/synopsys: dsi: Don't blindly call post_disable
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Hi Andrzej,

On 25/04/2019 13:13, Andrzej Hajda wrote:
> On 24.04.2019 16:22, Matt Redfearn wrote:
>> The DRM documentation states that post_disable is an optional callback.
>> As such an implementing device may not populate it. To avoid panicing
>> the kernel by calling a NULL function pointer, we should NULL check it
>> before blindy calling it.
>>
>> Signed-off-by: Matt Redfearn <matt.redfearn@thinci.com>
>
>> ---
>>
>> drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> index 38e88071363..0ee440216b8 100644
>> --- a/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> +++ b/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c
>> @@ -805,7 +805,8 @@ static void dw_mipi_dsi_bridge_post_disable(struct drm_bridge *bridge)
>> * This needs to be fixed in the drm_bridge framework and the API
>> * needs to be updated to manage our own call chains...
>> */
>> - dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
>> + if (dsi->panel_bridge->funcs->post_disable)
>> + dsi->panel_bridge->funcs->post_disable(dsi->panel_bridge);
>>
>
> Why not drm_bridge_post_disable ?

Ah - that seems like a nicer fix! Do you think the comment above
describing why this function pointer is called directly can be removed
as well if we go this route?

If someone calls drm_bridge_post_disable() on the Synposys DSI
drm_bridge it will go on to call post_disable on all other bridges in
the chain, in addition to us calling them here. Is it an issue to call
it multiple times?

Thanks,
Matt


>
>
> Regards
>
> Andrzej
>
>
>> if (dsi->slave) {
>> dw_mipi_dsi_disable(dsi->slave);
>
>
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