Re: [gphoto-devel] [PATCH, RFC]: Add a new camlib for ax203 based picture frames.

[Hans de G. <hde...@re...>]

Hi,

On 03/25/2010 10:31 AM, Marcus Meissner wrote:
> On Wed, Mar 24, 2010 at 07:17:20PM +0100, Hans de Goede wrote:
>> Hi,
>>
>> The attached patch makes it possible to download pictures from
>> / upload pictures to ax203 based picture frames
>>
>> It consists of 2 parts:
>> 1) st2205 camlib, st2205 access, "FAT" parsing, and decompress /
>>     compress code.
>>
>> 2) usbscsi port driver, this is a *Linux only* (for now) port driver
>>     for accessing devices which require sending custom scsi commands to
>>     an usb mass storage device (using the /dev/sg# device under Linux).
>>
>> I can commit this myself, but I would appreciate a quick review before
>> doing so.
>
> It looks good to me.
>

Thanks for the review.

> (I am kinda horrified by cloning a FAT fs driver, but well, it seems
> unavoidable ;)
>

Oh, I'm afraid you've misunderstood me there. Neither of these devices
actually uses an MSDOS FAT filesystem.

The interface to both devices is pretty raw, it provides direct read /
write access to the flash memory inside the picture frames. Both devices
have a table (at a constant offset) inside the flash, which describes
how many files are stored in the flash, and at which flash memory address
each picture is located (and in the case of the st2205 also a 10 character
name for the picture). I've dubbed these tables "FAT", but they have
nothing to do what so ever with msdos FAT filesystems, other then that
they are a table providing information on files. Sorry about the confusion.

I've updated the NEWS entry for the st2205 camlib to no longer mention
FAT, it now reads (in both trunk and 2_4 branch):

ST2205 Driver:
    * New Pictureframe driver from Hans de Goede. st2205 based frames present
      themselves as a regular usb mass storage device, but cannot be used
      as a normal disk! Communication with the device happens by a special
      protocol which consist of reading / writing sectors of the disk at
      certain magic offsets. Also included is a "usbdiskdirect" port driver,
      which allows the direct sector access the camlib for these devices needs.

I'll also add a NEWS entry for the new ax203 camlib.

Regards,

Hans