lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 4 Apr 2014 10:09:47 +0200 From: Geert Uytterhoeven <geert@...ux-m68k.org> To: Harini Katakam <harinikatakamlinux@...il.com> Cc: Mark Brown <broonie@...nel.org>, Grant Likely <grant.likely@...aro.org>, Rob Herring <robh+dt@...nel.org>, Pawel Moll <pawel.moll@....com>, Mark Rutland <mark.rutland@....com>, "ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>, Kumar Gala <galak@...eaurora.org>, linux-spi <linux-spi@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org> Subject: Re: [PATCH v2 2/2] devicetree: Add devicetree bindings documentation for Cadence SPI Hi Harini, On Fri, Apr 4, 2014 at 5:00 AM, Harini Katakam <harinikatakamlinux@...il.com> wrote: >>> + num-cs = /bits/ 16 <4>; >> >> What's going on with the /bits/ - is this something that's required for >> the property? > > The master->num-chipselect property is 16 bit but writing <4> here directly > leads to 0 being read in of_property_read (because it's big endian). > Instead using of property read u32 and then copying, we decided to do this. > This was discussed on v2 between Michal and Rob: >>>>> + num-chip-select = /bits/ 16 <4>; >>> >>> I was expecting you will comment this a little bit. :-) >>> Because all just reading this num-cs as 32bit and then >>> assigning this value to master->num_chipselect which is 16bit. >> >> Well, everyone else has that problem then. Obviously it takes a bit >> more care than just reading into a u32, but that is a kernel problem >> and not a problem of the binding. > They are not reading it directly with read_u32 but they are using > intermediate u32 value which is assigned to u16 which is fine. > This pattern is in most drivers(maybe all). > The point is if binding should or can't simplify driver code. > And from your reaction above I expect that it is up to driver > owner and binding doc how you want to do it. IMHO this "/bits/ 16" doesn't simplify the binding. As "num-cs" is a generic spi subsystem binding, it should not be restricted to 16 bits for the sake of a driver. As your hardware can drive 4 chip selects, you could represent it in 3 bits (don't!). Simple integers are 32 bit in DT, so use a temporary. Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists