[U-Boot] [PATCH 01/11] DM: add block device core

[Marek Vasut]

Dear Pavel Herrmann,

[...]

> > > blockctrl = AHCI, PIIX... whichever chip you have between SATA and PCI
> > > (or generally disk-bus and board-bus)
> > 
> > So this is for sata ? Or will it also by used for SD/USB flash discs?
> 
> no, blockctrl will be used for SATA, PATA, SCSI, and anything of the sort
> (device with several ports, block devices on said ports, ability to send
> read/write/query commands to devices on ports - definitely not USB,
> possibly also SD, but you probably want more operations from SD)

Why not USB flash ? Why not SD, what other stuff do you need for that? Is the 
API not misdesigned then?

> > > blockdev = disk, partition, SD card
> > 
> > Uh, let's say I understand (even if I don't see the correlation between
> > partition and SD card)
> 
> they are an ordered bunch of blocks with a "conventional" filesystem on
> them

You might want to do RAW reads, so why do you put filesystem into this context?

> > > - something that does basic checks
> > > (range, possibility of operation) and submits operations to correct
> > > parent (blockctrl, MMC controller, whatnot).
> > 
> > Ascii art might help here greatly (how these pieces fall together). I
> > think I do understand it though.
> 
> current code
> user -> FS -> offset calculation from partition info -> drivers/disk
> 
> new code
> user -> FS -> blockdev -> blockctrl (or USB or SD controller)

So your "blockctrl" should do the USB/SD/whatever muxing.

> partition blockdev does all the offset calculation and range check that FSs
> do now, and then submits the operation to the parent blockdev, which in
> turn submits it to blockctrl (or an SD controller in case of a SD card, or
> USB controller in case of a USB flash)

Make sure you document this in the next series.

> Pavel Herrmann

Best regards,
Marek Vasut