linux-kernel - Re: [PATCH] clk/rockchip: Use of_device_get_match

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Date:   Thu, 10 Mar 2022 17:22:15 +0100
From:   Heiko Stübner <heiko@...ech.de>
To:     cgel.zte@...il.com, mturquette@...libre.com,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Minghao Chi <chi.minghao@....com.cn>,
        Zeal Robot <zealci@....com.cn>
Subject: Re: [PATCH] clk/rockchip: Use of_device_get_match_data()

Am Mittwoch, 9. März 2022, 19:57:36 CET schrieb Stephen Boyd:
> Quoting cgel.zte@...il.com (2022-03-03 17:17:03)
> > From: Minghao Chi (CGEL ZTE) <chi.minghao@....com.cn>
> > 
> > Use of_device_get_match_data() to simplify the code.
> > 
> > Reported-by: Zeal Robot <zealci@....com.cn>
> > Signed-off-by: Minghao Chi (CGEL ZTE) <chi.minghao@....com.cn>
> > ---
> >  drivers/clk/rockchip/clk-rk3399.c | 8 +-------
> >  1 file changed, 1 insertion(+), 7 deletions(-)
> > 
> > diff --git a/drivers/clk/rockchip/clk-rk3399.c b/drivers/clk/rockchip/clk-rk3399.c
> > index 306910a3a0d3..b1b67bfb63b8 100644
> > --- a/drivers/clk/rockchip/clk-rk3399.c
> > +++ b/drivers/clk/rockchip/clk-rk3399.c
> > @@ -1634,14 +1634,8 @@ static const struct of_device_id clk_rk3399_match_table[] = {
> >  static int __init clk_rk3399_probe(struct platform_device *pdev)
> >  {
> >         struct device_node *np = pdev->dev.of_node;
> > -       const struct of_device_id *match;
> >         const struct clk_rk3399_inits *init_data;
> > -
> > -       match = of_match_device(clk_rk3399_match_table, &pdev->dev);
> > -       if (!match || !match->data)
> > -               return -EINVAL;
> > -
> > -       init_data = match->data;
> > +       init_data = of_device_get_match_data(&pdev->dev);
> 
> The translation doesn't look equivalent. Before we would bail out of
> probe if match data isn't there with an error. That isn't possible of
> course with further investigation but please make a note of this in the
> commit text to aid review.

We _do have_ Rockchip clock drivers serving multiple socs already
(rk3188+rk3066 for example) and as patterns are duplicated often from
one existing driver to a new one, I think it makes sense to have the
error handling done correctly.

So doing
	init_data = of_device_get_match_data(&pdev->dev);
	if (init_data)
		return -EINVAL;
as before.

If due to some strange coincidence the condition is triggered
this would cause a null-ptr-dereference with the direct call to
	init_data->scripts
below, which might or might not be hidden due to the (early-)console
being up yet, where with correct error handling a system might at
least come up to a point to complain about a missing clock driver.



> Also, please don't send new versions of
> patches in reply to previous versions of patches. It breaks my patch
> workflow. Thanks in advance.
> 
> >         if (init_data->inits)
> >                 init_data->inits(np);
> >
>