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Mon, 31 Aug 2020 09:07:52 -0400 IronPort-SDR: WWH8KCmrgdoq+d1DEwxjJAZwgueSvTdaTcIv6+cW9qy4gh9Ke0iPgHkIx2I34yCbTsLQgu88O3 aA03ptc9rYeg== X-IronPort-AV: E=McAfee;i="6000,8403,9729"; a="137015568" X-IronPort-AV: E=Sophos;i="5.76,375,1592895600"; d="scan'208";a="137015568" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 31 Aug 2020 06:07:51 -0700 IronPort-SDR: TftJ8w9CgwEpepgvlqjh3XEDiELLyGx/Hy2WvhqDPvnJ3ZZ54wTByK7sySJmLbWLi2O1D9WLlB PFk/m5rwAnng== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.76,375,1592895600"; d="scan'208";a="445707943" Received: from mattu-haswell.fi.intel.com (HELO [10.237.72.170]) ([10.237.72.170]) by orsmga004.jf.intel.com with ESMTP; 31 Aug 2020 06:07:49 -0700 Subject: Re: [PATCH v2] usb: xhci: add debugfs support for ep with stream To: Jun Li , "mathias.nyman@intel.com" Cc: "gregkh@linuxfoundation.org" , "linux-usb@vger.kernel.org" , dl-linux-imx References: <1594901321-6992-1-git-send-email-jun.li@nxp.com> From: Mathias Nyman Openpgp: preference=signencrypt Autocrypt: addr=mathias.nyman@linux.intel.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 18.8.2020 4.54, Jun Li wrote: > > >> -----Original Message----- >> From: Mathias Nyman >> Sent: Monday, August 17, 2020 7:48 PM >> To: Jun Li ; mathias.nyman@intel.com >> Cc: gregkh@linuxfoundation.org; linux-usb@vger.kernel.org; dl-linux-imx >> >> Subject: Re: [PATCH v2] usb: xhci: add debugfs support for ep with stream >> >> On 13.8.2020 12.57, Jun Li wrote: >>> Hi >>> >>>> -----Original Message----- >>>> From: Jun Li >>>> Sent: Thursday, July 16, 2020 8:40 PM >>>> To: mathias.nyman@intel.com >>>> Cc: gregkh@linuxfoundation.org; linux-usb@vger.kernel.org; >>>> dl-linux-imx >>>> Subject: [PATCH v2] usb: xhci: add debugfs support for ep with stream >>>> >>>> To show the trb ring of streams, use the exsiting ring files of bulk >>>> ep to show trb ring of one specific stream ID, which stream ID's trb >>>> ring will be shown, is controlled by a new debugfs file stream_id, >>>> this is to avoid to create a large number of dir for every allocate >>>> stream IDs, another debugfs file stream_context_array is created to show all >> the allocated stream context array entries. >>>> >>>> Signed-off-by: Li Jun >>>> --- >>>> chanages for v2: >>>> - Drop stream files remove, the stream files will be removed >>>> with ep dir removal, keep the ep but only remove streams >>>> actually does not make sense in current code. >>>> - Use the new_ring for show_ring pointer for non-zero ep. >>>> >>>> drivers/usb/host/xhci-debugfs.c | 112 >>>> +++++++++++++++++++++++++++++++++++++++- >>>> drivers/usb/host/xhci-debugfs.h | 10 ++++ >>>> drivers/usb/host/xhci.c | 1 + >>>> 3 files changed, 122 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/usb/host/xhci-debugfs.c >>>> b/drivers/usb/host/xhci-debugfs.c index 65d8de4..708585c 100644 >>>> --- a/drivers/usb/host/xhci-debugfs.c >>>> +++ b/drivers/usb/host/xhci-debugfs.c >>>> @@ -450,9 +450,14 @@ void xhci_debugfs_create_endpoint(struct xhci_hcd *xhci, >>>> if (!epriv) >>>> return; >>>> >>>> + if (dev->eps[ep_index].ring) >>>> + epriv->show_ring = dev->eps[ep_index].ring; >>>> + else >>>> + epriv->show_ring = dev->eps[ep_index].new_ring; >>>> + Ran some tests and the I suspect the above code causes issues. If an endpoint is dropped and added back the above code will store the old ring in epriv->show_ring as we have both a .ring and .new_ring present at that moment. Soon after this the old ring pointed to by .ring will be freed, and .ring = .new_ring will be set. Old code showed whatever ring buffer eps[i].ring pointer pointed to when the sysfs file was read, (as we saved the address, &eps[i].ring). I see now that it in theory it had a small gap before .ring = .new_ring was set where user could read the ring buffer and .ring would still be a NULL pointer. That needs to be fixed as well. I still like the old way of using double pointer more. xhci driver will also dig out the current ring from eps[i].ring, so I think we should as well. (in stream case it would be &ep->stream_info->stream_rings[stream_id]) -Mathias