Re: [PATCH 1/4] lib/fonts: Look up glyph data with font_data_glyph_buf()

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 01.06.26 um 13:18 schrieb Jocelyn Falempe:
> On 29/05/2026 16:01, Thomas Zimmermann wrote:
>> Add font_data_glyph_buf() to retrieve a character's glyph data or NULL
>> otherwise. Console fonts can currently contain 256 or 512 glyphs. The
>> kernel-internal characters are of type char, unsigned short or unsigned
>> int. Catch all of them by accepting unsigned int. Callers possibly have
>> to cast from signed to unsigned types to reach all glyphs in a font.
>
> Thanks, yes I missed to check font_data_num_glyphs(), and using signed 
> index is also problematic.
>
> Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>

Thanks for reviewing. I'll merge the series in a few days if no other 
comments come in.

Best regards
Thomas

>
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>>   include/linux/font.h |  3 +++
>>   lib/fonts/fonts.c    | 31 +++++++++++++++++++++++++++++++
>>   2 files changed, 34 insertions(+)
>>
>> diff --git a/include/linux/font.h b/include/linux/font.h
>> index 6845f02d739a..ea23b727388b 100644
>> --- a/include/linux/font.h
>> +++ b/include/linux/font.h
>> @@ -101,6 +101,9 @@ font_data_t *font_data_import(const struct 
>> console_font *font, unsigned int vpit
>>   void font_data_get(font_data_t *fd);
>>   bool font_data_put(font_data_t *fd);
>>   unsigned int font_data_size(font_data_t *fd);
>> +const unsigned char *font_data_glyph_buf(font_data_t *fd,
>> +                     unsigned int width, unsigned int vpitch,
>> +                     unsigned int c);
>>   bool font_data_is_equal(font_data_t *lhs, font_data_t *rhs);
>>   int font_data_export(font_data_t *fd, struct console_font *font, 
>> unsigned int vpitch);
>>   diff --git a/lib/fonts/fonts.c b/lib/fonts/fonts.c
>> index f5d5333450a0..4fc66722d00d 100644
>> --- a/lib/fonts/fonts.c
>> +++ b/lib/fonts/fonts.c
>> @@ -178,6 +178,37 @@ unsigned int font_data_size(font_data_t *fd)
>>   }
>>   EXPORT_SYMBOL_GPL(font_data_size);
>>   +static unsigned int font_data_num_glyphs(font_data_t *fd, unsigned 
>> int width, unsigned int height)
>> +{
>> +    return font_data_size(fd) / font_glyph_size(width, height);
>> +}
>> +
>> +/**
>> + * font_data_glyph_buf() - Returns the glyph for a specific 
>> character as raw bytes
>> + * @fd: The font data
>> + * @width: The glyph width in bits per scanline
>> + * @vpitch: The number of scanlines per glyph
>> + * @c: The character
>> + *
>> + * Glyphs start at fixed intervals within the font data. 
>> font_data_glyph_buf()
>> + * returns the glyph shape of the specified character. If no such glyph
>> + * exists in the font, it returns NULL.
>> + *
>> + * Returns:
>> + * The character's raw glyph shape, or NULL if no glyph exists for 
>> the character. The
>> + * provided buffer is read-only.
>> + */
>> +const unsigned char *font_data_glyph_buf(font_data_t *fd,
>> +                     unsigned int width, unsigned int vpitch,
>> +                     unsigned int c)
>> +{
>> +    if (c >= font_data_num_glyphs(fd, width, vpitch))
>> +        return NULL;
>> +
>> +    return font_data_buf(fd) + font_glyph_size(width, vpitch) * c;
>> +}
>> +EXPORT_SYMBOL_GPL(font_data_glyph_buf);
>> +
>>   /**
>>    * font_data_is_equal - Compares font data for equality
>>    * @lhs: Left-hand side font data
>

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)