On 7/31/23 11:21, Jason-JH Lin (林睿祥) wrote:
> Hi Eugen,
>
> Thanks for the reviews.
>
> On Fri, 2023-07-28 at 11:47 +0300, Eugen Hristev wrote:
>> Hi,
>>
>> On 7/27/23 19:41, Jason-JH.Lin wrote:
>>> Add checking the length of each data path before assigning drm
>>> private
>>> data into all_drm_priv array.
>>>
>>> Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195
>>> multi mmsys support")
>>> Signed-off-by: Jason-JH.Lin <[email protected]>
>>> ---
>>> drivers/gpu/drm/mediatek/mtk_drm_drv.c | 16 +++++++++++++---
>>> 1 file changed, 13 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>> b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>> index 249c9fd6347e..d2fb1fb4e682 100644
>>> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>> @@ -351,6 +351,7 @@ static bool mtk_drm_get_all_drm_priv(struct
>>> device *dev)
>>> {
>>> struct mtk_drm_private *drm_priv = dev_get_drvdata(dev);
>>> struct mtk_drm_private *all_drm_priv[MAX_CRTC];
>>> + struct mtk_drm_private *temp_drm_priv;
>>> struct device_node *phandle = dev->parent->of_node;
>>> const struct of_device_id *of_id;
>>> struct device_node *node;
>>> @@ -373,9 +374,18 @@ static bool mtk_drm_get_all_drm_priv(struct
>>> device *dev)
>>> if (!drm_dev || !dev_get_drvdata(drm_dev))
>>> continue;
>>>
>>> - all_drm_priv[cnt] = dev_get_drvdata(drm_dev);
>>> - if (all_drm_priv[cnt] && all_drm_priv[cnt]-
>>>> mtk_drm_bound)
>>> - cnt++;
>>> + temp_drm_priv = dev_get_drvdata(drm_dev);
>>> + if (temp_drm_priv) {
>>> + if (temp_drm_priv->mtk_drm_bound)
>>> + cnt++;
>>> +
>>> + if (temp_drm_priv->data->main_len)
>>> + all_drm_priv[0] = temp_drm_priv;
>>> + else if (temp_drm_priv->data->ext_len)
>>> + all_drm_priv[1] = temp_drm_priv;
>>> + else if (temp_drm_priv->data->third_len)
>>> + all_drm_priv[2] = temp_drm_priv;
>>> + }
>>
>> Previously the code was assigning stuff into all_drm_priv[cnt] and
>> incrementing it.
>> With your change, it assigns to all_drm_priv[0], [1], [2]. Is this
>> what
>> you intended ?
>
> Because dev_get_drvdata(drm_dev) will get the driver data by drm_dev.
> Each drm_dev represents a display path.
> e,g.
> drm_dev of "mediatek,mt8195-vdosys0" represents main path.
> drm_dev of "mediatek,mt8195-vdosys1" represents ext path.
>
> So we want to make sure all_drm_priv[] store the private data in
> the order of display path, such as:
> all_drm_priv[0] = the private data of main display
> all_drm_priv[1] = the private data of ext display
> all_drm_priv[2] = the private data of third display
If you have such a hard requirement for keeping elements in an array,
you are better having
drm_priv_main_display
drm_priv_ext_display
drm_priv_third_display
Keeping them indexed in a three elements array by having no logical
connection between the number [0,1,2] and the actual displays that you
want to save is a bit confusing.
One other option which I don't know if it's better or not is to have
macros to hide your indexed approach:
all_drm_priv[MAIN_DISPLAY] ...
etc.
>
>> If this loop has second run, you will reassign to all_drm_priv again
>> ?
>
> Because the previous code will store all_drm_priv[] in the order of
> mtk_drm_bind() was called.
>
> If drm_dev of ext path bound earlier than drm_dev of main path,
> all_drm_priv[] in mtk_drm_get_all_drm_priv() may be re-assigned like
> this:
> all_drm_priv[0]->all_drm_priv[0] = private data of ext path
> all_drm_priv[1]->all_drm_priv[0] = private data of ext path
> all_drm_priv[0]->all_drm_priv[1] = private data of main path
> all_drm_priv[1]->all_drm_priv[1] = private data of main path
>
> But we expect all_drm_priv[] be re-assigned like this:
> all_drm_priv[0]->all_drm_priv[0] = private data of main path
> all_drm_priv[1]->all_drm_priv[0] = private data of main path
> all_drm_priv[0]->all_drm_priv[1] = private data of ext path
> all_drm_priv[1]->all_drm_priv[1] = private data of ext path
This expectation does not appear to be really enforced in your code.
You have a driver that keeps an array with all_drm_priv[], in which
you can have main path or ext path. Then it's natural that they might
have whichever order in the array you are placing them into.
If you have a hard enforced order of keeping elements in your array,
then an indexed array is not the best option here.
You can either: move to a different type of array , with macros for
indexes into the array, or, store a second array/field which keeps the
index in which you saved each element.
This is just my opinion , by looking at your code.
>
>> I would expect you to take `cnt` into account.
>> Also, is it expected that all_drm_priv has holes in the array ?
>
> Each drm_dev will only called mtk_drm_bind() once, so all holes
> will be filled after all drm_dev has called mtk_drm_bind().
>
> Do you agree with this statement? :)
At the moment I cannot agree nor disagree, I don't know the code well
enough. But what I can say, is that you should not rely on future calls
of the function to fill up your array correctly.
>
> Regards,
> Jason-JH.Lin
>
>>
>> Eugen
>>
>>
>>
>>> }
>>>
>>> if (drm_priv->data->mmsys_dev_num == cnt) {
>>
>>
Hi Eugen,
On Mon, 2023-07-31 at 11:32 +0300, Eugen Hristev wrote:
> On 7/31/23 11:21, Jason-JH Lin (林睿祥) wrote:
> > Hi Eugen,
> >
> > Thanks for the reviews.
> >
snip...
> > > > + if (temp_drm_priv->data->main_len)
> > > > + all_drm_priv[0] =
> > > > temp_drm_priv;
> > > > + else if (temp_drm_priv->data->ext_len)
> > > > + all_drm_priv[1] =
> > > > temp_drm_priv;
> > > > + else if (temp_drm_priv->data-
> > > > >third_len)
> > > > + all_drm_priv[2] =
> > > > temp_drm_priv;
> > > > + }
> > >
> > > Previously the code was assigning stuff into all_drm_priv[cnt]
> > > and
> > > incrementing it.
> > > With your change, it assigns to all_drm_priv[0], [1], [2]. Is
> > > this
> > > what
> > > you intended ?
> >
> > Because dev_get_drvdata(drm_dev) will get the driver data by
> > drm_dev.
> > Each drm_dev represents a display path.
> > e,g.
> > drm_dev of "mediatek,mt8195-vdosys0" represents main path.
> > drm_dev of "mediatek,mt8195-vdosys1" represents ext path.
> >
> > So we want to make sure all_drm_priv[] store the private data in
> > the order of display path, such as:
> > all_drm_priv[0] = the private data of main display
> > all_drm_priv[1] = the private data of ext display
> > all_drm_priv[2] = the private data of third display
>
> If you have such a hard requirement for keeping elements in an
> array,
> you are better having
> drm_priv_main_display
> drm_priv_ext_display
> drm_priv_third_display
>
> Keeping them indexed in a three elements array by having no logical
> connection between the number [0,1,2] and the actual displays that
> you
> want to save is a bit confusing.
>
Yes, I think it was a bit confusing.
But we don't know which drm_priv will go into this function first and
we want to store all drm_priv into the same array.
So it has come to this.
> One other option which I don't know if it's better or not is to have
> macros to hide your indexed approach:
> all_drm_priv[MAIN_DISPLAY] ...
> etc.
>
Thanks for your advice.
I'll try to use macros to make it better and more readable.
> >
> >
> > > If this loop has second run, you will reassign to all_drm_priv
> > > again
> > > ?
> >
> > Because the previous code will store all_drm_priv[] in the order of
> > mtk_drm_bind() was called.
> >
> > If drm_dev of ext path bound earlier than drm_dev of main path,
> > all_drm_priv[] in mtk_drm_get_all_drm_priv() may be re-assigned
> > like
> > this:
> > all_drm_priv[0]->all_drm_priv[0] = private data of ext path
> > all_drm_priv[1]->all_drm_priv[0] = private data of ext path
> > all_drm_priv[0]->all_drm_priv[1] = private data of main path
> > all_drm_priv[1]->all_drm_priv[1] = private data of main path
> >
> > But we expect all_drm_priv[] be re-assigned like this:
> > all_drm_priv[0]->all_drm_priv[0] = private data of main path
> > all_drm_priv[1]->all_drm_priv[0] = private data of main path
> > all_drm_priv[0]->all_drm_priv[1] = private data of ext path
> > all_drm_priv[1]->all_drm_priv[1] = private data of ext path
>
> This expectation does not appear to be really enforced in your code.
> You have a driver that keeps an array with all_drm_priv[], in which
> you can have main path or ext path. Then it's natural that they
> might
> have whichever order in the array you are placing them into.
> If you have a hard enforced order of keeping elements in your array,
> then an indexed array is not the best option here.
> You can either: move to a different type of array , with macros for
> indexes into the array, or, store a second array/field which keeps
> the
> index in which you saved each element.
>
> This is just my opinion , by looking at your code.
>
There is another statement in mtk_drm_kms_init() like this:
for (i = 0; i < MAX_CRTC; i++) {
for (j = 0; j< private->data->mmsys_dev_num; j++) {
priv_n = private->all_drm_private[j];
if (i == 0 && priv_n->data->main_len) {
...
} else if (i == 1 && priv_n->data->ext_len) {
...
} else if (i == 2 && priv_n->data->third_len) {
...
}
}
}
So we need to make sure that each element in all_drm_priv[] has only
one path data:
all_drm_priv[0] has main_path data only
all_drm_priv[1] has ext_path data only
all_drm_priv[2] has third_path data only
I think it would take quite a bit of effort to change this array usage.
> > > I would expect you to take `cnt` into account.
> > > Also, is it expected that all_drm_priv has holes in the array ?
> >
> > Each drm_dev will only called mtk_drm_bind() once, so all holes
> > will be filled after all drm_dev has called mtk_drm_bind().
> >
> > Do you agree with this statement? :)
>
> At the moment I cannot agree nor disagree, I don't know the code
> well
> enough. But what I can say, is that you should not rely on future
> calls
> of the function to fill up your array correctly.
>
I agree with your opinion, but at the moment, I just want to fix the
issue first by having a less modification.
I'll try to use macros to replace the array index and I'll add more
description into commit message to express the current limitation in
mtk_drm_kms_init().
Thanks again~
Regards,
Jason-JH.Lin
> >
> > Regards,
> > Jason-JH.Lin
> >
> > >
> > > Eugen
> > >
> > >
> > >
> > > > }
> > > >
> > > > if (drm_priv->data->mmsys_dev_num == cnt) {
> > >
> > >
>
>