Path: csiph.com!goblin2!goblin.stu.neva.ru!aioe.org!bofh.it!news.nic.it!robomod From: Oliver Neukum Newsgroups: linux.kernel Subject: Re: [PATCH] USB: serial: cp210x: Workaround for cp2108 failure due to GET_LINE_CTL bug Date: Mon, 19 Oct 2015 11:20:02 +0200 Message-ID: References: X-Original-To: Konstantin Shkolnyy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 40 Organization: linux.* mail to news gateway X-Original-Cc: johan@kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org X-Original-Date: Mon, 19 Oct 2015 11:14:12 +0200 X-Original-Message-ID: <1445246052.1796.5.camel@suse.com> X-Original-References: <1444946786-18146-1-git-send-email-konstantin.shkolnyy@gmail.com> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1250493 On Thu, 2015-10-15 at 17:06 -0500, Konstantin Shkolnyy wrote: > cp2108 GET_LINE_CTL returns the 16-bit value with the 2 bytes swapped. > However, SET_LINE_CTL functions properly. When the driver tries to modify > the register, it reads it, modifies some bits and writes back. Because the > read bytes were swapped, this often results in an invalid value to be written. > In turn, this causes cp2108 respond with a stall. The stall sometimes doesn't > clear properly and cp2108 starts responding to following valid commands also > with stalls, effectively failing. Just a remark. > > @@ -865,18 +888,53 @@ static void cp210x_break_ctl(struct tty_struct *tty, int break_state) > > static int cp210x_startup(struct usb_serial *serial) > { > + struct usb_serial_port *port; > struct usb_host_interface *cur_altsetting; > struct cp210x_serial_private *spriv; > + unsigned int line_ctl; > + int err; > + > + /* We always expect a single port only */ > + if (serial->num_ports != 1) { > + dev_err(&serial->dev->dev, "%s - expected 1 port, found %d\n", > + __func__, serial->num_ports); > + return -EINVAL; > + } Why do you introduce this new check? It has no obvious connect with the subject of this fix. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/