Hi Am 09.02.22 um 14:26 schrieb Javier Martinez Canillas:
Hello Thomas, Thanks a lot for your feedback. On 2/9/22 13:51, Thomas Zimmermann wrote:Hi[snip]+ + if (xb == pixels - 1 && end_offset) + end = end_offset;end_offset should be called end_len, because it is the number of bits in the final byte; but not the offset of the final bit.Indeed. [snip]+void drm_fb_gray8_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *vaddr, + const struct drm_framebuffer *fb, + const struct drm_rect *clip)[snip]Do you really need that function. It's not exported and if it's not otherwise used, I'd just remove it. We don't keep unused interfaces around.At the end after your suggestion of doing line-per-line conversions it is not needed, but since I already typed it and we were talking about adding other formats besides the fake XRGB8888 as an optimization (R8 for grayscale and Dx or something like that for reversed mono), I thought that would be useful to have it as a helper. Also other drivers that want to advertise a R8 format could just use it and not having to add their own helper. But I'm happy to drop it in v4 if you think that's better to not have unused helpers. It could be taken from this patch-set anyways if someone wants to wire the needed support for R8.
I think, policy is to not keep unused code around.
[snip]+ + /* + * The reversed mono destination buffer contains 1 bit per pixel + * and destination scanlines have to be in multiple of 8 pixels. + */ + if (!dst_pitch) + dst_pitch = DIV_ROUND_UP(linepixels, 8);I'd do a warn_once if (dst_pitch % 8 != 0).Agreed. I'll add a warning an mention that will be rounded up.+ + /* + * The cma memory is write-combined so reads are uncached. + * Speed up by fetching one line at a time.I once had a patchset that adds caching information to struct dma_buf_map (soon to be named struct iosys_map). Blitting helpers would be able to enable/disable this optimization as needed. However, your driver doesn't use CMA. It's backed by SHMEM. Do you really want to keep that code in?It doesn't but the repaper does. And since the plan was to make that driver to use the helper instead of having their own, I wanted to also make sure that would work well with CMA.
That makes sense then.
+ */ + src32 = kmalloc(len_src32, GFP_KERNEL); + if (!src32) + return; + + /* + * Copies are done line-by-line, allocate an intermediate + * buffer to copy the gray8 lines and then convert to mono. + */ + gray8 = kmalloc(linepixels, GFP_KERNEL); + if (!gray8) + goto free_src32;If might be faster to allocate both buffers in one step and set the pointers into the allocated buffer.Not sure I got this. Do you mean to have a single buffer with length linepixels + len_src32 and point src32 and gray8 to the same buffer ?
That's the idea. I don't know the exact overhead for kalloc(), but at least the in userspace, malloc() in hot code paths is not a good idea. There's usually some searching for free space involved.
In the long term, we could add a field in struct drm_framebuffer to keep such buffers around for reuse.
+ + /* + * For damage handling, it is possible that only parts of the source + * buffer is copied and this could lead to start and end pixels that + * are not aligned to multiple of 8. + * + * Calculate if the start and end pixels are not aligned and set the + * offsets for the reversed mono line conversion function to adjust. + */ + start_offset = clip->x1 % 8; + end_offset = clip->x2 % 8;end_len, again. If you have 1 single bit set in the final byte, the offset is 0, but the length is 1.Agreed, will change it too.
Feel free to add my Reviewed-by: Thomas Zimmermann <tzimmermann@xxxxxxx> to the next version. Best regards Thomas
Best regards,
-- 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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