Hi, On 23 May 2017 at 16:18, Andreas Färber <afaer...@suse.de> wrote: > Hi Heiko, > > Am 23.05.2017 um 23:27 schrieb Heiko Stuebner: >> Am Dienstag, 23. Mai 2017, 17:14:19 CEST schrieb Tom Rini: >>> On Tue, May 23, 2017 at 11:03:23PM +0200, Mark Kettenis wrote: >>>>> From: Heiko Stuebner <he...@sntech.de> >>>>> Date: Tue, 23 May 2017 22:29:33 +0200 >>>>> >>>>> Hi Kever, Tom, >>>>> >>>>> Am Dienstag, 23. Mai 2017, 14:32:44 CEST schrieb Kever Yang: >>>>>> This is not from kernel, seems the kernel mmc driver does not >>>>>> support aliases now, >>>>>> >>>>>> thought I hope they both support the aliases for ordering. >>>>> >>>>> there was a lengthy discussion about the pros and cons of ordering >>>>> mmc devices last year [0]. >>>>> >>>>> With the outcome that explicit ordering via aliases is not desired >>>>> and the argument being that mmc devices are not so different from >>>>> usb storage or scsi/sata devices whose ordering is random all the time. >>>> >>>> Aren't you intepreting the outcome of that discussion a bit too >>>> broadly tough? That discussion seems to reject an explicit ordering >>>> of mmc device names in the Linux kernel, mainly because better >>>> mechanisms exist to refer to a particular device than its device >>>> name/number. But that doesn't preclude having a meaningful set of >>>> aliases for certain boards if there is some sort of canonical boot >>>> order or if devices are actually numbered on a board? >>>> >>>> In OpenFirmware the primary purpose of these aliases is to specify >>>> which device to boot from. >> >> readding the lkml-link for the above: >> [0] https://lkml.org/lkml/2016/4/29/621 >> >> >> As for that being to broad, wasn't that why Tom suggested moving that >> to a -u-boot.dtsi file, because while generally not desired, it may >> benefit uboot to get some sane boot order / type marks (emmc, sd-card), >> but doesn't influence the core devicetree files that should ideally be >> synced from the kernel or wherever? > > I think you're mixing three very distinct topics here: > a) Whether Linux drivers should use aliases for ordering. > b) Whether to add aliases in the DT. > c) Sync'ing .dts files from Linux vs. local changes. > > I don't see what's wrong with b) as it is useful as a shorthand for > access to a particular node, e.g. for U-Boot's fdt commands. > > Tom's point is that if a certain change is not in the Linux .dts and is > needed for U-Boot, it should go into a U-Boot specific .dtsi file, so > that the change doesn't get overwritten with the next .dts update from > Linux. > In the UEFI boot path we rely on a recent upstream-compatible DT being > provided by U-Boot if none is installed by the OS in a way U-Boot can > load, so the .dts will need to be re-sync'ed later on even if it doesn't > affect U-Boot drivers. Therefore the commit messages also need to > indicate where the .dts comes from, to avoid regressions on re-sync from > different trees.
Further to that, I think U-Boot needs the aliases because we refer to devices by number. At a future date if U-Boot moves away from this to named devices, we can revisit it. But so far as I can tell, without the aliases, U-Boot cannot operate in a reliable, repeatable manner. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot
