> -----Original Message----- > From: geert.uytterhoeven@xxxxxxxxx [mailto:geert.uytterhoeven@xxxxxxxxx] > On Behalf Of Geert Uytterhoeven > Sent: Tuesday, March 18, 2014 4:56 PM > To: Hou Zhiqiang-B48286 > Cc: Mark Brown; linux-spi@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; > rob.herring@xxxxxxxxxxx; pawel.moll@xxxxxxx; mark.rutland@xxxxxxx; > ijc+devicetree@xxxxxxxxxxxxxx; galak@xxxxxxxxxxxxxx; > grant.likely@xxxxxxxxxxxx; Wood Scott-B07421; Hu Mingkai-B21284 > Subject: Re: [PATCH 2/2] spi/fsl-lib: Get the SPI controller bus number > from DTS > > On Tue, Mar 18, 2014 at 8:40 AM, B48286@xxxxxxxxxxxxx > <B48286@xxxxxxxxxxxxx> wrote: > >> > > The DT already has support for specifying flash layouts, can't > >> > > those be used (for example via chosen if they're not fixed for the > board)? > >> > > Or if it's just picking the correct filesystem then UUIDs and > >> > > labels are the standard way to do things. > >> > >> > The DT specifying flash layouts is ok. There is another way to make > >> > the flash layouts using command line, but it is not safe because of > >> > the dynamic bus_num. It is not the reason that the way of DT is > >> > supported flash layouts, to live the other way unsafe, right? > >> > >> This sounds to me like we need a better way of talking about flash > >> device names on the Linux command line rather than a way to fix the > >> bus number - for example, being able to refer to them using a fixed > >> property like the physical address. Being able to refer to devices > >> via an alias assigned in the DT would also be useful (and more > >> readable), I think there may already be a mechanism for doing that > >> which would need to be plumbed in but I'm not 100% sure. > > > > The bus number is the variable designed to distinguish one spi > > controller from others. Why spi controller's physical address must be > > use instead of bus number? > > Because the bus number is dynamic, while the physical address doesn't > change, so it can be used to uniqely identify the device before booting > the kernel. > Cfr. "spi1" vs. "e6e20000.spi". > The precondition of dynamic bus number is initial it with -1 in the controller driver. But now I need a reasonable bus number, I don't want a dynamic one. Why does use the controller's physical address to take the role of bus number to distinguish controllers. > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux- > 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 > ��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
