linux-kernel - Re: [PATCH v1] fbdev: sm712fb: fix an issue about iounmap for a wrong address

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Date:   Thu, 23 Apr 2020 14:14:48 +0200
From:   Markus Elfring <Markus.Elfring@....de>
To:     Dejin Zheng <zhengdejin5@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Teddy Wang <teddy.wang@...iconmotion.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v1] fbdev: sm712fb: fix an issue about iounmap for a wrong
 address

> the sfb->fb->screen_base is not save the value get by iounmap() when
> the chip id is 0x720.

I suggest to improve this change description.
How did you determine relevant differences for the mentioned chip model?


> so iounmap() for address sfb->fb->screen_base is not right.

Will another imperative wording become helpful here?


…
> +++ b/drivers/video/fbdev/sm712fb.c
> @@ -1429,6 +1429,8 @@  static int smtc_map_smem(struct smtcfb_info *sfb,
>  static void smtc_unmap_smem(struct smtcfb_info *sfb)
>  {
>  	if (sfb && sfb->fb->screen_base) {
> +		if (sfb->chip_id == 0x720)
> +			sfb->fb->screen_base -= 0x00200000;
>  		iounmap(sfb->fb->screen_base);

How do you think about to use descriptive identifiers for
the shown constants?

Would you like to clarify any related software analysis approaches?

Regards,
Markus