linux-kernel - Re: [PATCH] staging: most: dim2: read done_buffers count locally from HDM channel

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Date:   Tue, 18 Oct 2022 11:31:44 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     Julia Lawall <julia.lawall@...ia.fr>
Cc:     outreachy@...ts.linux.dev, gregkh@...uxfoundation.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kumarpraveen@...ux.microsoft.com, saurabh.truth@...il.com
Subject: Re: [PATCH] staging: most: dim2: read done_buffers count locally
 from HDM channel

On Tue, Oct 18, 2022 at 07:35:29AM +0200, Julia Lawall wrote:
>
>
> On Tue, 18 Oct 2022, Deepak R Varma wrote:
>
> > On Mon, Oct 17, 2022 at 10:56:03PM +0200, Julia Lawall wrote:
> > >
> > >
> > > On Tue, 18 Oct 2022, Deepak R Varma wrote:
> > >
> > > > The done_buffer count can be directly read from HDM channel instead of
> > > > calling the dim_get_channel_state function. This change also results in
> > > > obsoleting the dim_channel_state local structure variable.
> > > >
> > > > Signed-off-by: Deepak R Varma <drv@...lo.com>
> > > > ---
> > > >
> > > > PLEASE NOTE: I have only built the module on my machine, but have not tested it.
> > > > I am not sure how to test this change. I am willing to test it with appropriate
> > > > guidance provided I have the necessary hardware.
> > >
> > > For non experts, maybe it would be helpful to explain what motivated you
> > > to do this?
> >
> > I was actually trying to understand the implementation of this module to
> > determine if I can replace BUG_ON calls by WARN_ON_ONCE. A "ctrl+]" navigation
> > took me to this function and I started wondering about why the function call
> > would be necessary. Hence the change.
>
> OK, I agree with you that this story might not be super interesting.
>
> But the log message still seems too concise.  You have acquired some
> knowledge about why this changeis correct, but that knowledge is not at
> all reflected in the log message.  Try to explain in more detail why the
> function call is not necessary.

Sounds good. I will update the patch log and resubmit the patch.
Thank you,

./drv

>
> julia
>
> >
> > While reading the Documentation under dim2 directory, I realised this module may
> > need a specialised hardware for testing [automotive???]. Hence I was not sure
> > how to test the same.
> >
> > Are you suggesting I mention this in the patch description (the motivation)?
> >
> > Thank you,
> > ./drv
> >
> > >
> > > julia
> > >
> > > >
> > > >  drivers/staging/most/dim2/dim2.c | 3 +--
> > > >  1 file changed, 1 insertion(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/staging/most/dim2/dim2.c b/drivers/staging/most/dim2/dim2.c
> > > > index ab72e11ac5ab..4c1f27898a29 100644
> > > > --- a/drivers/staging/most/dim2/dim2.c
> > > > +++ b/drivers/staging/most/dim2/dim2.c
> > > > @@ -259,7 +259,6 @@ static void retrieve_netinfo(struct dim2_hdm *dev, struct mbo *mbo)
> > > >  static void service_done_flag(struct dim2_hdm *dev, int ch_idx)
> > > >  {
> > > >  	struct hdm_channel *hdm_ch = dev->hch + ch_idx;
> > > > -	struct dim_ch_state_t st;
> > > >  	struct list_head *head;
> > > >  	struct mbo *mbo;
> > > >  	int done_buffers;
> > > > @@ -271,7 +270,7 @@ static void service_done_flag(struct dim2_hdm *dev, int ch_idx)
> > > >
> > > >  	spin_lock_irqsave(&dim_lock, flags);
> > > >
> > > > -	done_buffers = dim_get_channel_state(&hdm_ch->ch, &st)->done_buffers;
> > > > +	done_buffers = hdm_ch->ch.done_sw_buffers_number;
> > > >  	if (!done_buffers) {
> > > >  		spin_unlock_irqrestore(&dim_lock, flags);
> > > >  		return;
> > > > --
> > > > 2.30.2
> > > >
> > > >
> > > >
> > > >
> > > >
> >
> >
> >
>