linux-kernel - Re: [PATCH v5 2/3] VT: Add KDFONTINFO ioctl

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Message-ID: <f3e4e710-a392-4924-94c1-6dd52c803f9a@gmx.de>
Date: Thu, 25 Apr 2024 13:35:41 +0200
From: Helge Deller <deller@....de>
To: Alexey Gladkov <legion@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Jiri Slaby <jirislaby@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
 kbd@...ts.linux.dev, linux-api@...r.kernel.org, linux-fbdev@...r.kernel.org,
 linux-serial@...r.kernel.org
Subject: Re: [PATCH v5 2/3] VT: Add KDFONTINFO ioctl

On 4/25/24 13:06, Alexey Gladkov wrote:
> On Thu, Apr 25, 2024 at 12:33:28PM +0200, Helge Deller wrote:
>>>>> diff --git a/include/uapi/linux/kd.h b/include/uapi/linux/kd.h
>>>>> index 8ddb2219a84b..68b715ad4d5c 100644
>>>>> --- a/include/uapi/linux/kd.h
>>>>> +++ b/include/uapi/linux/kd.h
>>>>> @@ -185,6 +185,20 @@ struct console_font {
>>>>>
>>>>>     #define KD_FONT_FLAG_DONT_RECALC 	1	/* Don't recalculate hw charcell size [compat] */
>>>>>
>>>>> +/* font information */
>>>>> +
>>>>> +#define KD_FONT_INFO_FLAG_LOW_SIZE	_BITUL(0) /* 256 */
>>>>> +#define KD_FONT_INFO_FLAG_HIGH_SIZE	_BITUL(1) /* 512 */
>>>>
>>>> Do we really need those bits?
>>>> You set a default min/max font size in con_font_info() above,
>>>> and all drivers can override those values.
>>>> So, there are always min/max sizes available.
>>>
>>> These bits are not about the minimum and maximum glyph size, but about the
>>> number of glyphs in the font.
>>>
>>> Maybe this is an overkill, but sticon has this check:
>>>
>>> if ((w < 6) || (h < 6) || (w > 32) || (h > 32) || (vpitch != 32)
>>>       || (op->charcount != 256 && op->charcount != 512))
>>>
>>> [ to be honest, I don’t know why this driver doesn’t accept a glyph of
>>> width 4 ]
>>
>> I think there was no technical limitation when I added that.
>> It's just that the font would be so small...
>
> If so, then I can remove min_height/min_width from the ioctl structure.
> And most likely the flags can also be left empty since at the moment all
> drivers support 512.

Yes, I think that's ok.

Helge