linux-kernel - Re: [PATCH v2 4/4] vt: coherence validation code for the unicode screen buffer

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Message-ID: <CAHp75VfG_4zw+NPuHTUyH-gzdktiCKVcnWcwo0D_fAgfPbdk+A@mail.gmail.com>
Date:   Tue, 19 Jun 2018 01:01:59 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dave Mielke <Dave@...lke.cc>,
        Samuel Thibault <samuel.thibault@...-lyon.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 4/4] vt: coherence validation code for the unicode
 screen buffer

On Sun, Jun 17, 2018 at 10:07 PM, Nicolas Pitre
<nicolas.pitre@...aro.org> wrote:
> Make sure the unicode screen buffer matches the video screen content.
> This is provided for debugging convenience and disabled by default.

> +#define VC_UNI_SCREEN_DEBUG 0

> +       if (!VC_UNI_SCREEN_DEBUG || !uniscr)
> +               return;

Hmm... Interesting. I would rather go with
#ifdef ..._DEBUG
...
#else
return;
#endif

It will relax requirement on how to define _DEBUG. I don't recall I
see something like you proposing in the kernel for the same purpose.

> +
> +       WARN_CONSOLE_UNLOCKED();
> +
> +       /*
> +        * Make sure our unicode screen translates into the same glyphs
> +        * as the actual screen. This is brutal indeed.
> +        */
> +       p = (unsigned short *)vc->vc_origin;
> +       mask = vc->vc_hi_font_mask | 0xff;
> +       for (y = 0; y < vc->vc_rows; y++) {
> +               char32_t *line = uniscr->lines[y];
> +               for (x = 0; x < vc->vc_cols; x++) {
> +                       u16 glyph = scr_readw(p++) & mask;
> +                       char32_t uc = line[x];
> +                       int tc = conv_uni_to_pc(vc, uc);
> +                       if (tc == -4)
> +                               tc = conv_uni_to_pc(vc, 0xfffd);
> +                       if (tc == -4)
> +                               tc = conv_uni_to_pc(vc, '?');
> +                       if (tc != glyph)

> +                               pr_notice("%s: mismatch at %d,%d: "
> +                                         "glyph=%#x tc=%#x\n", __func__,
> +                                         x, y, glyph, tc);

Don't split format string in printk(). checkpatch will not warn on longer lines.

> +               }
> +       }

-- 
With Best Regards,
Andy Shevchenko