Messages in this thread | | | Date | Fri, 28 Apr 2023 14:59:32 +0200 | Subject | Re: [PATCH v2 5/5] fbdev: Define framebuffer I/O from Linux' I/O functions | From | Thomas Zimmermann <> |
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Hi Robin, Geert
Am 28.04.23 um 14:27 schrieb Geert Uytterhoeven: > On Fri, Apr 28, 2023 at 2:18 PM Robin Murphy <robin.murphy@arm.com> wrote: >> On 2023-04-28 10:27, Thomas Zimmermann wrote: >>> Implement framebuffer I/O helpers, such as fb_read*() and fb_write*() >>> with Linux' regular I/O functions. Remove all ifdef cases for the >>> various architectures. >>> >>> Most of the supported architectures use __raw_() I/O functions or treat >>> framebuffer memory like regular memory. This is also implemented by the >>> architectures' I/O function, so we can use them instead. >>> >>> Sparc uses SBus to connect to framebuffer devices. It provides respective >>> implementations of the framebuffer I/O helpers. The involved sbus_() >>> I/O helpers map to the same code as Sparc's regular I/O functions. As >>> with other platforms, we can use those instead. >>> >>> We leave a TODO item to replace all fb_() functions with their regular >>> I/O counterparts throughout the fbdev drivers. >>> >>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> >>> --- >>> include/linux/fb.h | 63 +++++++++++----------------------------------- >>> 1 file changed, 15 insertions(+), 48 deletions(-) >>> >>> diff --git a/include/linux/fb.h b/include/linux/fb.h >>> index 08cb47da71f8..4aa9e90edd17 100644 >>> --- a/include/linux/fb.h >>> +++ b/include/linux/fb.h >>> @@ -15,7 +15,6 @@ >>> #include <linux/list.h> >>> #include <linux/backlight.h> >>> #include <linux/slab.h> >>> -#include <asm/io.h> >>> >>> struct vm_area_struct; >>> struct fb_info; >>> @@ -511,58 +510,26 @@ struct fb_info { >>> */ >>> #define STUPID_ACCELF_TEXT_SHIT >>> >>> -// This will go away >>> -#if defined(__sparc__) >>> - >>> -/* We map all of our framebuffers such that big-endian accesses >>> - * are what we want, so the following is sufficient. >>> +/* >>> + * TODO: Update fbdev drivers to call the I/O helpers directly and >>> + * remove the fb_() tokens. >>> */ >>> - >>> -// This will go away >>> -#define fb_readb sbus_readb >>> -#define fb_readw sbus_readw >>> -#define fb_readl sbus_readl >>> -#define fb_readq sbus_readq >>> -#define fb_writeb sbus_writeb >>> -#define fb_writew sbus_writew >>> -#define fb_writel sbus_writel >>> -#define fb_writeq sbus_writeq >>> -#define fb_memset sbus_memset_io >>> -#define fb_memcpy_fromfb sbus_memcpy_fromio >>> -#define fb_memcpy_tofb sbus_memcpy_toio >>> - >>> -#elif defined(__i386__) || defined(__alpha__) || defined(__x86_64__) || \ >>> - defined(__hppa__) || defined(__sh__) || defined(__powerpc__) || \ >>> - defined(__arm__) || defined(__aarch64__) || defined(__mips__) >>> - >>> -#define fb_readb __raw_readb >>> -#define fb_readw __raw_readw >>> -#define fb_readl __raw_readl >>> -#define fb_readq __raw_readq >>> -#define fb_writeb __raw_writeb >>> -#define fb_writew __raw_writew >>> -#define fb_writel __raw_writel >>> -#define fb_writeq __raw_writeq >> >> Note that on at least some architectures, the __raw variants are >> native-endian, whereas the regular accessors are explicitly >> little-endian, so there is a slight risk of inadvertently changing >> behaviour on big-endian systems (MIPS most likely, but a few old ARM >> platforms run BE as well). > > Also on m68k, when ISA or PCI are enabled. > > In addition, the non-raw variants may do some extras to guarantee > ordering, which you do not need on a frame buffer. > > So I'd go for the __raw_*() variants everywhere.
Ok, makes sense. But it also means that we won't be able to remove the fb_() helpers. If we go with this proposal, I'll add your comments to the header file, so it's clear why they're still there.
Best regards Thomas
> > Gr{oetje,eeting}s, > > Geert >
-- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg) [unhandled content-type:application/pgp-signature] | |