On Friday 27 November 2015 18:28:50 Nicolas Pitre wrote: > On Fri, 27 Nov 2015, Arnd Bergmann wrote: > > > I don't mind creating the /proc/atags compatibility hack from the kernel > > for a DT based N700 kernel, as long as we limit it as much as we can > > to the machines that need it. Leaving a board file for the N700 in place > > that contains the procfs code (and not much more) seems reasonable > > here, as we are talking about a board specific hack and the whole point > > appears to be running unmodified user space. > > > > Regarding how to get the data into the kernel in the first place, my > > preferred choice would still be to have an intermediate bootloader > > such as pxa-impedance-matcher, but I won't complain if others are > > happy enough about putting it into the ATAGS compat code we already > > have, as long as it's limited to the boards we know need it. > > Assuming you have a N700 board file for special procfs code, then why > not getting at the atags in memory where the bootloader has put them > directly from that same board file? This way it'll really be limited to > the board we know needs it and the special exception will be contained > to that one file. Amongst the machine specific hooks, there is one that > gets invoked early during boot before those atags are overwritten. I didn't realize this was possible, as we don't know the atags pointer when we instead get a DTB pointer. However you are right: the board file knows exactly that the atag_offset is 0x100, so we can grab it from there, and that will make the implementation really easy and contained to a single file that has access to the atags and that can create the /proc/atags file for it. Arnd -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
