> On 08/15/2013 08:54 PM, Caizhiyong wrote: > >>> +blkdevparts=<blkdev-def>[;<blkdev-def>] > >>> + <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>] > >>> + <partdef> := <size>[@<offset>](part-name) > >>> + > >>> +<blkdev-id> > >>> + block device disk name, embedded device used fixed block device, > >>> + it's disk name also fixed. such as: mmcblk0, mmcblk1, mmcblk0boot0. > >> > >> The device-name isn't always fixed. > >> > >> For example, what if there are multiple SDHCI controllers, one hosting a > >> fixed eMMC device and the other an SD card? It's quite typical for the > >> eMMC's device name (which is likely what should be affected by this > >> feature) to be mmcblk0 when no SD card is present, yet be mmcblk1 when > >> an SD card is present. Is there a more precise/stable way to define > >> which device the command-line option applies to? > > > > Yes. Fixed is for single controller. > > For multiple controllers, currently, there is not a simple way. > > I tend to do something in the eMMC driver, such as initialize order, > > but I have not tried. > > There have been proposals before to try and create a fixed naming for > the controllers (or rather the block devices they generate...) but > they've been rejected. I don't think we should rely on being able to do > that. > > >>> + > >>> +<offset> > >>> + partition start address, in bytes. > >>> + > >>> +(part-name) > >>> + partition name, kernel send uevent with "PARTNAME". application can > >>> create > >>> + a link to block device partition with the name "PARTNAME". > >>> + user space application can access partition by partition name. > >> > >> Do partitions usually have a PARTNAME attribute when probed through > >> normal mechanisms like MBR? If so, I guess this is fine. > >> > >> Perhaps we can just use , as the delimiter for all fields, rather than > >> special-casing part-name to use (), so: > >> > >> size,offset,partname,size,offset,partname,... > >> > >> The partname field could easily be empty if not needed. > > > > If no need partname, your bootargs are mmcblk0:1G,1G,1G,... > > Well, you always need the offset too. I don't think there's any harm in > forcing all fields to be specified in all cases; it makes the whole > system much more regular and less error-prone. > > Alternatively, use a different separator between fields for a given > partition, and between partitions, e.g.: > > size,offset,partname;size,offset,partname > > That way, you know that if you see a ; you're looking at a new > partition, and hence the partname field need not always be specified. > Although, if you want to specify a partname but not an offset you'd > still need empty fields, so just requiring all fields to always be > present still seems safest to me.
I just follow MTD cmdline partition format.(reference drivers/mtd/cmdlinepart.c) There are many pitfalls in using this partition format, the designer is more consideration its ease of use, rather than safe. There is an other conversation: https://lkml.org/lkml/2013/8/3/16 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
