Re: [PATCH v2 1/3] usb: gadget: f_fs: virtual address mapping

From: Robert Baldyga
Date: Mon Jul 28 2014 - 01:53:23 EST

On 07/25/2014 04:18 PM, Michal Nazarewicz wrote:
> On Fri, Jul 25 2014, Robert Baldyga wrote:
>> This patch adds virtual endpoint address mapping to functionfs.
>> So far endpoint addresses given by user through endpoint descriptors
>> were ignored, and replaced by physical endpoint addresses. Endpoint
>> address in wIndex field of setup requesti, addressed to endpoint, was
>> the physical endpoint address, and names of files in functionfs
>> directory was numered in order, and were the same as indexes of
>> ffs_epfile in epfile array. In result user has no way to indicate
>> which file in functionfs is associated with which particular
>> requested endpoint. He also didn't know which endpoint is recipient
>> of setup request.
> Couldn't that be solved by simply providing the mapping to user space?

There would be only small differences in code (add mapping instead of
changing file names) so why would we not want do it in more intuitive way?

>> There was also one more problem - if endpoint addresses in descriptors
>> were non-consecutive, there were created redundant files, which could
>> cause problems in kernel, when user tryed to read/write to them.
>> It was result of fact that maximum endpoint address was taken as
>> total number of endpoints in funciton.
> This is kinda unrelated though. I mean it's a separate bug.

Yes, but it can be fixed by the way, as a side effect, so there is no
sense (and probably no simple way) to move it into separate patch.

>> This patch solves this problems by introducing virtual endpoint address
>> mapping. Now each function has separate endpoint address space. Numbers
>> of endpoint files in functionfs and addresses in setup requests are
>> mapped to addresses choosen by user in endpoint descriptors.
>> It also introduces additional testing if desctiptors given by user are
>> consistent - if number of endpoints and their addresses in each speed
>> are the same.
>> Signed-off-by: Robert Baldyga <r.baldyga@xxxxxxxxxxx>
>> ---
>> drivers/usb/gadget/f_fs.c | 78 +++++++++++++++++++++++++++++++++++++++--------
>> drivers/usb/gadget/u_fs.h | 2 ++
>> 2 files changed, 68 insertions(+), 12 deletions(-)

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