From: Thomas Zimmermann <tzimmermann@suse.de>
To: Javier Martinez Canillas <javierm@redhat.com>,
airlied@linux.ie, daniel@ffwll.ch, deller@gmx.de,
maxime@cerno.tech, sam@ravnborg.org, msuchanek@suse.de,
mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org,
geert@linux-m68k.org, mark.cave-ayland@ilande.co.uk
Cc: linux-fbdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v2 06/10] drm/simpledrm: Move some functionality into fwfb helper library
Date: Wed, 27 Jul 2022 10:24:44 +0200 [thread overview]
Message-ID: <623cde06-62ec-c8be-0f0e-2fd900c2359a@suse.de> (raw)
In-Reply-To: <c411480b-27b2-8c0b-534f-bbabd8018577@redhat.com>
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Hi
Am 25.07.22 um 18:23 schrieb Javier Martinez Canillas:
> On 7/20/22 16:27, Thomas Zimmermann wrote:
>> Move some of simpledrm's functionality into a helper library. Other
>> drivers for firmware-provided framebuffers will also need functions
>> to handle fixed modes and color formats, or update the back buffer.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>> ---
>
> Nice patch!
TBH it took me 3 tries to get something done for this library and I'm
still not happy with the result. I want to share code between simpledrm
and ofdrm, but that turns out to be harder then expected. A good part of
this code appears to belong into other libraries (you also mentioned
this below).
I don't want to duplicated code between simpledrm and ofdrm without
reason, but I expect that this library will somewhen be refactored and
dissolved into existing libraries.
>
> [...]
>
>> +
>> +/**
>> + * DOC: overview
>> + *
>> + * The Firmware Framebuffer library FWFB provides helpers for devices with
>> + * fixed-mode backing storage. It helps drivers to export a display mode of
>> + * te correct size and copy updates to the backing storage.
>
> the
>
> it is "backing storage" or "backing store" ? I always thought that storage was
> used for non-volatile media while "store" could be volatile and non-volatile.
Why store? Isn't that a little shop for fashion or groceries? I'm no
native speaker; I can't tell if either implies that we're sending
pictures to a warehouse or bakery. :)
Would 'back buffer' (in contrast to 'shadow buffer') be clear?
>
> [...]
>
>> +/**
>> + * drm_fwfb_init - Initializes an fwfb buffer
>> + * @fwfb: fwfb buffer
>> + * @screen_base: Address of the backing buffer in kernel address space
>> + * @width: Number of pixels per scanline
>> + * @height: Number of scanlines
>> + * @format: Color format
>> + * @pitch: Distance between two consecutive scanlines in bytes
>> + *
>> + * Returns:
>> + * 0 on success, or a negative errno code otherwise.
>> + */
>> +int drm_fwfb_init(struct drm_fwfb *fwfb, struct iosys_map *screen_base,
>> + unsigned int width, unsigned int height,
>> + const struct drm_format_info *format, unsigned int pitch)
>> +{
>> + fwfb->screen_base = *screen_base;
>> + fwfb->mode = drm_fwfb_mode(width, height);
>> + fwfb->format = format;
>
> It seems a little bit arbitrary to me that format is the only field that's
> a pointer and the other ones are embedded into the struct drm_fwfb. Any
> reason for that or is just a consequence of how types were used by the
> simpledrm_device_create() function before that code moved into helpers ?
Format is constant and comes from statically initialized memory in
drm_fourcc.c. I'd expect to be able to compare formats by comparing the
pointers. Copying the format here would break the assumption.
>
> [...]
>
>> +static bool is_listed_fourcc(const uint32_t *fourccs, size_t nfourccs, uint32_t fourcc)
>> +{
>> + const uint32_t *fourccs_end = fourccs + nfourccs;
>> +
>> + while (fourccs < fourccs_end) {
>> + if (*fourccs == fourcc)
>> + return true;
>> + ++fourccs;
>> + }
>> + return false;
>> +}
>
> This seems a helper that could be useful besides the drm_fwfb_helper.c file.
>
> I believe patches 1-6 shouldn't wait for the others in this series and could
> just be merged when ready. Patches 7-10 can follow later.
Yeah, I'd like to move patches 1 to 5 into a new series for merging.
Patch 6 is only useful for ofdrm and as I said, maybe there's a better
solution then this library. I'd rather keep it here for now.
Best regards
Thomas
>
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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next prev parent reply other threads:[~2022-07-27 8:24 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-20 14:27 [PATCH v2 00/10] drm: Add driver for PowerPC OF displays Thomas Zimmermann
2022-07-20 14:27 ` [PATCH v2 01/10] drm/simpledrm: Remove mem field from device structure Thomas Zimmermann
2022-07-25 14:48 ` Javier Martinez Canillas
2022-07-20 14:27 ` [PATCH v2 02/10] drm/simpledrm: Inline device-init helpers Thomas Zimmermann
2022-07-25 15:01 ` Javier Martinez Canillas
2022-07-27 7:50 ` Thomas Zimmermann
2022-07-27 9:30 ` Javier Martinez Canillas
2022-07-20 14:27 ` [PATCH v2 03/10] drm/simpledrm: Remove pdev field from device structure Thomas Zimmermann
2022-07-25 15:02 ` Javier Martinez Canillas
2022-07-20 14:27 ` [PATCH v2 04/10] drm/simpledrm: Compute framebuffer stride if not set Thomas Zimmermann
2022-07-21 14:46 ` Geert Uytterhoeven
2022-07-25 15:13 ` Javier Martinez Canillas
2022-07-27 7:53 ` Thomas Zimmermann
2022-08-11 17:23 ` Daniel Vetter
2022-08-11 18:26 ` Thomas Zimmermann
2022-08-11 18:27 ` Thomas Zimmermann
2022-09-06 19:16 ` Daniel Vetter
2022-07-20 14:27 ` [PATCH v2 05/10] drm/simpledrm: Convert to atomic helpers Thomas Zimmermann
2022-07-25 15:46 ` Javier Martinez Canillas
2022-07-27 7:58 ` Thomas Zimmermann
2022-07-20 14:27 ` [PATCH v2 06/10] drm/simpledrm: Move some functionality into fwfb helper library Thomas Zimmermann
2022-07-25 16:23 ` Javier Martinez Canillas
2022-07-27 8:24 ` Thomas Zimmermann [this message]
2022-07-27 9:39 ` Javier Martinez Canillas
2022-07-20 14:27 ` [PATCH v2 07/10] drm/ofdrm: Add ofdrm for Open Firmware framebuffers Thomas Zimmermann
2022-07-26 13:17 ` Javier Martinez Canillas
2022-09-21 11:41 ` Thomas Zimmermann
2022-07-20 14:27 ` [PATCH v2 08/10] drm/ofdrm: Add CRTC state Thomas Zimmermann
2022-07-26 13:36 ` Javier Martinez Canillas
2022-09-21 11:45 ` Thomas Zimmermann
2022-07-20 14:27 ` [PATCH v2 09/10] drm/ofdrm: Add per-model device function Thomas Zimmermann
2022-07-26 13:38 ` Javier Martinez Canillas
2022-07-26 14:40 ` Michal Suchánek
2022-07-26 19:22 ` Javier Martinez Canillas
2022-07-27 8:33 ` Thomas Zimmermann
2022-08-05 0:22 ` Benjamin Herrenschmidt
2022-09-21 12:37 ` Thomas Zimmermann
2022-07-20 14:27 ` [PATCH v2 10/10] drm/ofdrm: Support color management Thomas Zimmermann
2022-07-26 13:49 ` Javier Martinez Canillas
2022-07-27 8:41 ` Thomas Zimmermann
2022-07-27 9:45 ` Javier Martinez Canillas
2022-08-05 0:29 ` Benjamin Herrenschmidt
2022-08-05 0:19 ` Benjamin Herrenschmidt
2022-09-21 12:55 ` Thomas Zimmermann
2022-09-21 16:48 ` Geert Uytterhoeven
2022-09-22 6:42 ` Thomas Zimmermann
2022-09-22 7:28 ` Maxime Ripard
2022-09-22 8:06 ` Thomas Zimmermann
2022-07-28 11:13 ` [PATCH v2 00/10] drm: Add driver for PowerPC OF displays Michael Ellerman
2022-07-28 11:31 ` Michal Suchánek
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