linux-kernel - Re: [PATCH v2 2/3] usb: gadget: f_fs: add ioctl returning ep descriptor

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Date:	Mon, 28 Jul 2014 08:42:44 +0200
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	Michal Nazarewicz <mina86@...a86.com>,
	Robert Baldyga <r.baldyga@...sung.com>, balbi@...com
Cc:	gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, andrzej.p@...sung.com
Subject: Re: [PATCH v2 2/3] usb: gadget: f_fs: add ioctl returning ep descriptor

Hello,

On 2014-07-25 16:15, Michal Nazarewicz wrote:
> On Fri, Jul 25 2014, Robert Baldyga wrote:
>> This patch introduces ioctl named FUNCTIONFS_ENDPOINT_DESC, which
>> returns endpoint descriptor to userspace. It works only if function
>> is active.
> I would argue that user space should never need to know the real
> descriptor.  Is this ioctl needed for anything in particular?

Some proprietary broken usb protocols might embed real physical endpoint
(or interface) number into the data stream. In such case functionfs driver
is unable to do proper endpoint/interface number fixup.

>
>> Signed-off-by: Robert Baldyga <r.baldyga@...sung.com>
>> ---
>>   drivers/usb/gadget/f_fs.c           | 17 +++++++++++++++++
>>   include/uapi/linux/usb/functionfs.h |  6 ++++++
>>   2 files changed, 23 insertions(+)
>>
>> diff --git a/drivers/usb/gadget/f_fs.c b/drivers/usb/gadget/f_fs.c
>> index 490b30f..a2e18cc 100644
>> --- a/drivers/usb/gadget/f_fs.c
>> +++ b/drivers/usb/gadget/f_fs.c
>> @@ -1031,6 +1031,23 @@ static long ffs_epfile_ioctl(struct file *file, unsigned code,
>>   		case FUNCTIONFS_ENDPOINT_REVMAP:
>>   			ret = epfile->ep->num;
>>   			break;
>> +		case FUNCTIONFS_ENDPOINT_DESC:
>> +		{
>> +			int desc_idx;
>> +			struct usb_endpoint_descriptor *desc;
>> +
>> +			if (epfile->ffs->gadget->speed == USB_SPEED_SUPER)
>> +				desc_idx = 2;
>> +			else if (epfile->ffs->gadget->speed == USB_SPEED_HIGH)
>> +				desc_idx = 1;
>> +			else
>> +				desc_idx = 0;
>> +			desc = epfile->ep->descs[desc_idx];
>> +			ret = copy_to_user((void *)value, desc, sizeof(*desc));
>> +			if (ret)
>> +				ret = -EFAULT;
>> +			break;
>> +		}
>>   		default:
>>   			ret = -ENOTTY;
>>   		}
>> diff --git a/include/uapi/linux/usb/functionfs.h b/include/uapi/linux/usb/functionfs.h
>> index 1dc473a..1ab6f06 100644
>> --- a/include/uapi/linux/usb/functionfs.h
>> +++ b/include/uapi/linux/usb/functionfs.h
>> @@ -197,6 +197,12 @@ struct usb_functionfs_event {
>>    */
>>   #define	FUNCTIONFS_ENDPOINT_REVMAP	_IO('g', 129)
>>   
>> +/*
>> + * Returns endpoint descriptor. In funciton is not active returns -ENODEV.
>> + */
>> +#define	FUNCTIONFS_ENDPOINT_DESC	_IOR('g', 130, \
>> +					     struct usb_endpoint_descriptor)
>> +
>>   
>>   
>>   #endif /* _UAPI__LINUX_FUNCTIONFS_H__ */
>> -- 
>> 1.9.1

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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