From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Date: Tue, 08 Jan 2013 10:37:13 -0700 Subject: [U-Boot] Selecting from multiple device trees at runtime In-Reply-To: References: <50EB0D92.2020707@cumulusnetworks.com> <20130107201240.52C9120DA7E@gemini.denx.de> <50EB4A4C.9050201@cumulusnetworks.com> <50EC4C79.3050806@wwwdotorg.org> Message-ID: <50EC5949.7030708@wwwdotorg.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: u-boot@lists.denx.de On 01/08/2013 09:51 AM, Simon Glass wrote: > Hi Stephen, > > On Tue, Jan 8, 2013 at 8:42 AM, Stephen Warren wrote: >> On 01/07/2013 08:16 PM, Simon Glass wrote: >>> Hi, >>> >>> On Mon, Jan 7, 2013 at 2:21 PM, Curt Brune wrote: >>>> >>>> >>>> On 01/07/2013 12:12 PM, Wolfgang Denk wrote: >>>>> >>>>> Dear Curt Brune, >>>>> >>>>> In message <50EB0D92.2020707@cumulusnetworks.com> you wrote: >>>>>> >>>>>> >>>>>> What I would love is to have a single multi-file uImage I could use on >>>>>> all my platforms. The idea is to introduce a new image type that is a >>>>>> list of device tree blobs. >>>>> >>>>> >>>>> In addition to the file system based approach suggested by Stephen, >>>>> you should have a look into using FIT images (see doc/uImage.FIT/ ). >>>>> One of the reasons for creating these was to deal with situations >>>>> exactly as you describe... >>>> >>>> >>>> I think that will work perfectly. Thank you for the suggestion. >>> >>> Note also there is code in mainline now to select the correct FDT from >>> a list of them in a FIT. based on the model name. Then it can pass >>> this to the kernel. So if you have a way of getting the model name in >>> U-Boot, it might just work. >> >> Hmmm. What's the model name compared against? U-Boot board name variable >> would be nice! > > At the moment it compares against the model in the U-Boot FDT > (CONFIG_OF_CONTROL). When flashing a board, you pack u-boot.bin with > the selected .dtb file containing this model name. Then when U-Boot > runs it knows what its model is. > > You could do what you describe, but it is then a compile-time check, I think. > > There could be other ways to decide on the model name, such as looking > at strapping GPIOs, for example: > > static const char *detect_model(void) > { > if (gpio_get_value(36)) > return "snow"; > else > return "flax"; > } Right - I believe the TI guys introduced the board_name variable or similar to indicate the runtime-detected board ID for this purpose (whereas the board variable I introduced is the board U-Boot was compiled for). It'd be nice to be able to select a DTB from FIT based on $board_name instead of U-Boot's own DTB's model given all this. Do the sub-images in the FIT image have filenames that could be selected as e.g. ${soc}-${board}.dtb? Using $board or $board_name would also help where U-Boot doesn't use a DT itself.