Re: [PATCH v6] usb-storage,uas: use host helper to generate driver info

[Milan Broz <gmazyland@gmail.com>]

Hi Greg,

On 1/28/24 02:50, Greg KH wrote:
> On Sun, Nov 05, 2023 at 07:20:47PM +0100, Milan Broz wrote:
>> The USB mass storage quirks flags can be stored in driver_info in
>> a 32-bit integer (unsigned long on 32-bit platforms).
>> As this attribute cannot be enlarged, we need to use some form
>> of translation of 64-bit quirk bits.
>>
>> This problem was discussed on the USB list
>> https://lore.kernel.org/linux-usb/f9e8acb5-32d5-4a30-859f-d4336a86b31a@gmail.com/
>>
>> The initial solution to use a static array extensively increased the size
>> of the kernel module, so I decided to try the second suggested solution:
>> generate a table by host-compiled program and use bit 31 to indicate
>> that the value is an index, not the actual value.
>>
>> This patch adds a host-compiled program that processes unusual_devs.h
>> (and unusual_uas.h) and generates files usb-ids.c and usb-ids-uas.c
>> (for pre-processed USB device table with 32-bit device info).
>> These files also contain a generated translation table for driver_info
>> to 64-bit values.
>>
>> The translation function is used only in usb-storage and uas modules; all
>> other USB storage modules store flags directly, using only 32-bit flags.
>>
>> For 64-bit platforms, where unsigned long is 64-bit, we do not need to
>> convert quirk flags to 32-bit index; the translation function there uses
>> flags directly.
>>
>> Signed-off-by: Milan Broz <gmazyland@gmail.com>
> 
> I see the need for this, but why now?  We haven't run out of ids yet
> have we?  Do we need to add another one?

I had a patchset that needed a new flag; that was the motivation.
However, after a discussion with SCSI people, it needed to be done differently,
and I had no time to rewrite it yet.

In the meantime, the flag transition patch was split from the series.

If you want to merge it now, I can easily rebase & fix gitignore issue.

Or it can wait for the next first real user.

Just I have spent a lot of time with this, so no need to repeat this exercise, though :-)

Thanks,
Milan
  
> Also, after building, I get the following files marked by git as needed
> to be added to the tree, so perhaps you also need a .gitignore file:
> 
> $ git status
> On branch work-testing
> Untracked files:
>    (use "git add <file>..." to include in what will be committed)
> 	drivers/usb/storage/mkflags
> 	drivers/usb/storage/usb-ids-uas.c
> 	drivers/usb/storage/usb-ids.c
> 
> thanks,
> 
> greg k-h