Date: Sat, 15 Oct 2011 22:03:04 +0530 From: "Jayachandran C." <jchandra@freebsd.org> To: Nathan Whitehorn <nwhitehorn@freebsd.org> Cc: Rafal Jaworowski <raj@semihalf.com>, Marcel Moolenaar <marcel@freebsd.org>, FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: [RFC] FDT fix for 64 bit platforms Message-ID: <CA%2B7sy7DRTM%2Bmgxx4ogEwttLtsaVyWA5XQ4bnfJ54rQLmHZ34Pw@mail.gmail.com> In-Reply-To: <4E99A319.20801@freebsd.org> References: <CA%2B7sy7AhU7WLuabx6HCtUgvEtUHWBmGe-eP=N8L9VknM65r-mg@mail.gmail.com> <4E989C28.3030606@freebsd.org> <CA%2B7sy7Ba6zrRGQuon%2B7FPk8EhgnpYLWTGv0EAPy0pdRXJfc3ZQ@mail.gmail.com> <4E99A319.20801@freebsd.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sat, Oct 15, 2011 at 8:43 PM, Nathan Whitehorn <nwhitehorn@freebsd.org> wrote: > On 10/15/11 01:12, Jayachandran C. wrote: >> >> On Sat, Oct 15, 2011 at 2:01 AM, Nathan Whitehorn >> <nwhitehorn@freebsd.org> =A0wrote: >>> >>> On 10/14/11 14:10, Jayachandran C. wrote: >>>> >>>> I'm planning commit this -CURRENT if there an no objections. >>>> >>>> In the current implementation, phandle is used to store a pointer to >>>> the location inside the device tree. =A0Since phandle_t is u32, this >>>> will not work on 64 bit platforms. With this fix, the phandle is the >>>> offset from the start of device tree pointer 'fdtp', which will be 32 >>>> bit. >>>> >>>> Review or testing from device tree users will be welcome. >>>> >>>> JC. >>> >>> Why not use offsets into the FDT rather than full pointers? I believe >>> having >>> phandles greater than 32 bits violates the FDT spec, and declaring that >>> the >>> FDT can't itself be larger than 4 GB seems reasonable. >> >> I am actually using the offset from the beginning of FDT (fdtp) as >> phandle. =A0I cannot use the usual fdt offset (after off_dt_struct) as >> phandle, because in that case offset of 0 is valid, but phandle 0 >> should not be valid. > > Why shouldn't phandle 0 be valid? The invalid phandle is -1. This is one = of > the problems with our existing FDT code -- it makes all kinds of wrong > assumptions like this about IEEE 1275. Well, the existing FDT code returns 0 as the invalid handle and I do not want to change that in this commit. If the return value is really wrong, we will need a bigger exercise to change the return value and fix any callers which are affected by that change. JC.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CA%2B7sy7DRTM%2Bmgxx4ogEwttLtsaVyWA5XQ4bnfJ54rQLmHZ34Pw>