Hi Stephen, On Mon, Apr 4, 2011 at 11:09 PM, Stephen Warren <swarren@xxxxxxxxxx> wrote: > Chris et. al., > > I'm working on an ARM system that contains at least two MMC/SD devices; > specifically the board has an internal MMC device, and an SD card slot, > although the SoC has four MMC/SD hosts IIRC. > > The kernel's naming of these devices is dynamic. If the SD card is not > plugged in, the internal MMC is always known as mmcblock0. If the SD card > is plugged in too, sometimes the internal MMC is mmcblk0 and sometimes it's > mmcblk1. I assume this is timing related; 2.6.37 usually seemed to name > them "in order", whereas 2.6.38 usually seems to name them "backwards". > > This causes problems with the bootloader scripts I'm using, which assumes > that the internal MMC is always device 0 and the SD slot is always device 1, > and hence provides kernel command-line argument root=/dev/mmcblk0p3 or > root=/dev/mmcblk1p3 based on whether it booted from SD or internal MMC (SD > is searched for a valid image first by the bootloader). Just follow this thread which discusses the same but for OMAP4 controller http://www.mail-archive.com/linux-omap@xxxxxxxxxxxxxxx/msg47853.html One solution could be make your internal MMC always registered as mmcblk0 and the removable one as next device. Regards, Kishore > > This could be solved by naming the kernel MMC devices statically based on > the host controller, rather than dynamically based on the first available > ID when the actual storage is detected. The patch below implements this. > > Is this patch conceptually acceptable for the MMC driver? Obviously, a > complete patch would need to also remove the dev_use structure etc. > > Another solution might be for the kernel command-line to specify the > filesystem UUID, rather than a device node. However, this entails much more > work for the bootloader. I'm not sure whether U-Boot can do this right now? > And actually, the filesystem images I'm using don't always have a UUID by > dDefault IIRC. > > diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c > index bfc8a8a..5131b02 100644 > --- a/drivers/mmc/card/block.c > +++ b/drivers/mmc/card/block.c > @@ -581,7 +581,7 @@ static struct mmc_blk_data *mmc_blk_alloc(struct mmc_card *card) > struct mmc_blk_data *md; > int devidx, ret; > > - devidx = find_first_zero_bit(dev_use, max_devices); > + devidx = card->host->index; > if (devidx >= max_devices) > return ERR_PTR(-ENOSPC); > __set_bit(devidx, dev_use); > > Thanks for any feedback. > > -- > nvpublic > > -- > To unsubscribe from this list: send the line "unsubscribe linux-mmc" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
