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[209.85.219.178]) by smtp.gmail.com with ESMTPSA id j11-20020a37a00b000000b0067b436faccesm2008675qke.122.2022.03.08.08.13.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 08 Mar 2022 08:13:51 -0800 (PST) Received: by mail-yb1-f178.google.com with SMTP id j2so38858735ybu.0; Tue, 08 Mar 2022 08:13:51 -0800 (PST) X-Received: by 2002:a25:dfd3:0:b0:629:24ff:eab0 with SMTP id w202-20020a25dfd3000000b0062924ffeab0mr10980528ybg.613.1646756030721; Tue, 08 Mar 2022 08:13:50 -0800 (PST) MIME-Version: 1.0 References: <20220214133710.3278506-1-javierm@redhat.com> <20220214133710.3278506-3-javierm@redhat.com> In-Reply-To: <20220214133710.3278506-3-javierm@redhat.com> From: Geert Uytterhoeven Date: Tue, 8 Mar 2022 17:13:38 +0100 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v6 2/6] drm/format-helper: Add drm_fb_xrgb8888_to_mono_reversed() To: Javier Martinez Canillas Cc: Linux Kernel Mailing List , Linux Fbdev development list , Andy Shevchenko , Daniel Vetter , Thomas Zimmermann , Sam Ravnborg , DRI Development , Maxime Ripard , =?UTF-8?Q?Noralf_Tr=C3=B8nnes?= , Daniel Vetter , David Airlie , Maarten Lankhorst , Maxime Ripard Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org Hi Javier, On Mon, Feb 14, 2022 at 2:37 PM Javier Martinez Canillas wrote: > Add support to convert from XR24 to reversed monochrome for drivers that > control monochromatic display panels, that only have 1 bit per pixel. > > The function does a line-by-line conversion doing an intermediate step > first from XR24 to 8-bit grayscale and then to reversed monochrome. > > The drm_fb_gray8_to_mono_reversed_line() helper was based on code from > drivers/gpu/drm/tiny/repaper.c driver. > > Signed-off-by: Javier Martinez Canillas > Reviewed-by: Thomas Zimmermann > Reviewed-by: Andy Shevchenko Thanks for your patch, which is now commit bcf8b616deb87941 ("drm/format-helper: Add drm_fb_xrgb8888_to_mono_reversed()") in drm/drm-next. > --- a/drivers/gpu/drm/drm_format_helper.c > +++ b/drivers/gpu/drm/drm_format_helper.c > @@ -12,9 +12,11 @@ > #include > #include > > +#include > #include > #include > #include > +#include > #include > > static unsigned int clip_offset(const struct drm_rect *clip, unsigned int pitch, unsigned int cpp) > @@ -591,3 +593,111 @@ int drm_fb_blit_toio(void __iomem *dst, unsigned int dst_pitch, uint32_t dst_for > return -EINVAL; > } > EXPORT_SYMBOL(drm_fb_blit_toio); > + > +static void drm_fb_gray8_to_mono_reversed_line(u8 *dst, const u8 *src, unsigned int pixels, "pixels" is not the number of pixels to process, but the number of bytes in the monochrome destination buffer. > + unsigned int start_offset, unsigned int end_len) > +{ > + unsigned int xb, i; > + > + for (xb = 0; xb < pixels; xb++) { > + unsigned int start = 0, end = 8; > + u8 byte = 0x00; > + > + if (xb == 0 && start_offset) > + start = start_offset; > + > + if (xb == pixels - 1 && end_len) > + end = end_len; > + > + for (i = start; i < end; i++) { > + unsigned int x = xb * 8 + i; > + > + byte >>= 1; > + if (src[x] >> 7) > + byte |= BIT(7); > + } > + *dst++ = byte; > + } The above is IMHO very hard to read. I think it can be made simpler by passing the total number of pixels to process instead of "pixels" (which is bytes) and "end_len". > +} > + > +/** > + * drm_fb_xrgb8888_to_mono_reversed - Convert XRGB8888 to reversed monochrome > + * @dst: reversed monochrome destination buffer > + * @dst_pitch: Number of bytes between two consecutive scanlines within dst > + * @src: XRGB8888 source buffer > + * @fb: DRM framebuffer > + * @clip: Clip rectangle area to copy > + * > + * DRM doesn't have native monochrome support. > + * Such drivers can announce the commonly supported XR24 format to userspace > + * and use this function to convert to the native format. > + * > + * This function uses drm_fb_xrgb8888_to_gray8() to convert to grayscale and > + * then the result is converted from grayscale to reversed monohrome. > + */ > +void drm_fb_xrgb8888_to_mono_reversed(void *dst, unsigned int dst_pitch, const void *vaddr, > + const struct drm_framebuffer *fb, const struct drm_rect *clip) > +{ > + unsigned int linepixels = drm_rect_width(clip); > + unsigned int lines = clip->y2 - clip->y1; drm_rect_height(clip)? > + unsigned int cpp = fb->format->cpp[0]; > + unsigned int len_src32 = linepixels * cpp; > + struct drm_device *dev = fb->dev; > + unsigned int start_offset, end_len; > + unsigned int y; > + u8 *mono = dst, *gray8; > + u32 *src32; > + > + if (drm_WARN_ON(dev, fb->format->format != DRM_FORMAT_XRGB8888)) > + return; > + > + /* > + * 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); This is not correct when clip->x1 is not a multiple of 8 pixels. Should be: DIV_ROUND_UP(linepixels + clip->x1 % 8, 8); > + > + drm_WARN_ONCE(dev, dst_pitch % 8 != 0, "dst_pitch is not a multiple of 8\n"); This triggers for me: dst_pitch = 1. Which is perfectly fine, when flashing an 8-pixel wide cursor ;-) > + > + /* > + * The cma memory is write-combined so reads are uncached. > + * Speed up by fetching one line at a time. > + * > + * Also, format conversion from XR24 to reversed monochrome > + * are done line-by-line but are converted to 8-bit grayscale > + * as an intermediate step. > + * > + * Allocate a buffer to be used for both copying from the cma > + * memory and to store the intermediate grayscale line pixels. > + */ > + src32 = kmalloc(len_src32 + linepixels, GFP_KERNEL); > + if (!src32) > + return; > + > + gray8 = (u8 *)src32 + len_src32; > + > + /* > + * 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_len = clip->x2 % 8; > + > + vaddr += clip_offset(clip, fb->pitches[0], cpp); > + for (y = 0; y < lines; y++) { > + src32 = memcpy(src32, vaddr, len_src32); > + drm_fb_xrgb8888_to_gray8_line(gray8, src32, linepixels); > + drm_fb_gray8_to_mono_reversed_line(mono, gray8, dst_pitch, > + start_offset, end_len); > + vaddr += fb->pitches[0]; > + mono += dst_pitch; > + } > + > + kfree(src32); > +} > +EXPORT_SYMBOL(drm_fb_xrgb8888_to_mono_reversed); Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds