> -----Original Message----- > From: Tony Lindgren [mailto:tony@xxxxxxxxxxx] > Sent: Monday, September 22, 2014 3:17 PM > To: Krzysztof Opasiak > Cc: 'Matt Porter'; linux-usb@xxxxxxxxxxxxxxx; Stanislaw Wadas; > Andrzej Pietrasiewicz; Marek Szyprowski; Karol Lewandowski; > philippedeswert@xxxxxxxxx > Subject: Re: [PATCH] libusbg: Fix usbg_disable_gadget to actually > clear the UDC > > * Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx> [140922 01:07]: > > Dear Tony, > > > > > -----Original Message----- > > > From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb- > > > owner@xxxxxxxxxxxxxxx] On Behalf Of Tony Lindgren > > > Sent: Saturday, September 20, 2014 5:51 PM > > > To: Matt Porter > > > Cc: linux-usb@xxxxxxxxxxxxxxx > > > Subject: [PATCH] libusbg: Fix usbg_disable_gadget to actually > clear > > > the UDC > > > > > > Currently usbg_disable_gadget() does not actually write > anything > > > to UDC to clear it and the configured UDC name stays there. > > > > > > > No, udc name doesn't stay there due to O_TRUNC flag which is > always used > > for writing in usbg_write_string(). With this flag we don't need > to > > write new line to file because size of file is set to 0 while > opening. > > > > Summing up: > > > > open("/sys/kernel/config/usb_gadget/g1/UDC", > O_WRONLY|O_CREAT|O_TRUNC, > > 0666) = 3 > > close(3) = 0 > > > > causes unbind, so everything works fine. > > Hmm not clearing for me doing this afterwards: > > # cat /sys/kernel/config/usb_gadget/g1/UDC > musb-hdrc.0.auto > > The UDC name stays there and won't get cleared. > > Am I missing something? Please forgive me, I have checked it once again and you are right. I thought that truncate flag works on configfs in a similar way than on others fs but I was wrong. This flag simply does nothing and you have definitely found a bug. I was certain sure that this function works fine due to gadget-vid-pid-remove example. In this simple program gadget is disabled before removing. I had in my mind that it is impossible to modify a gadget if it is bound to any udc. This example worked fine so I assumed that usbg_disable_gadget() also works fine. I have look into configfs composite gadget source and there I have found some surprise: /* * ideally I would like to forbid to unlink functions while a gadget is * bound to an UDC. Since this isn't possible at the moment, we simply * force an unbind, the function is available here and then we can * remove the function. */ mutex_lock(&gi->lock); if (gi->udc_name) unregister_gadget(gi); WARN_ON(gi->udc_name); This means that it is currently possible to remove function binding on enabled gadget and it will cause unbind. This is why usbg_rm_gadget() also worked fine without proper usbg_disable_gadget(). Summing up, Your patch fix an important bug. Its form is good for me. I have checked it and it works fine. You may add: Reviewed-by: Krzysztof Opasiak <k.opasiak@xxxxxxxxxxx> If it is going about Matt Porter activity, he is not responding for mails or patches since April. I have github-fork of libusbg [1] with latest source (my master is 35 commits ahead of libusbg/master and some devel branches are even more). All patches which are intended for libusbg (sent on a list or from pull requests) are merged there after review. Please let me also notice that your patch has been also merged into my master. Thank you for fixing this issue. Foot notes: 1 - https://github.com/kopasiak/libusbg -- Best Regards, Krzysztof Opasiak Samsung R&D Institute Poland Samsung Electronics k.opasiak@xxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
