From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Subject: [v3] usb/hcd: Send a uevent signaling that the host controller had died From: Raul E Rangel Message-Id: <20190418152902.GA185502@google.com> Date: Thu, 18 Apr 2019 09:29:02 -0600 To: Greg Kroah-Hartman Cc: Alan Stern , Guenter Roeck , linux-usb@vger.kernel.org, Guenter Roeck , Oliver Neukum , Daniel Kurtz , zwisler@chromium.org, Sebastian Andrzej Siewior , Martin Blumenstingl , Dmitry Torokhov , linux-kernel , "Gustavo A. R. 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2019 08:29:07 -0700 (PDT) Date: Thu, 18 Apr 2019 09:29:02 -0600 From: Raul Rangel To: Greg Kroah-Hartman Cc: Alan Stern , Guenter Roeck , linux-usb@vger.kernel.org, Guenter Roeck , Oliver Neukum , Daniel Kurtz , zwisler@chromium.org, Sebastian Andrzej Siewior , Martin Blumenstingl , Dmitry Torokhov , linux-kernel , "Gustavo A. R. Silva" , Miquel Raynal , Johan Hovold , Mathias Nyman , Raul Rangel Subject: Re: [PATCH v3] usb/hcd: Send a uevent signaling that the host controller had died Message-ID: <20190418152902.GA185502@google.com> References: <20190418065141.GB12503@kroah.com> <20190418143048.GA11555@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline In-Reply-To: <20190418143048.GA11555@kroah.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Message-ID: <20190418152902.EbOs-z9PHLmkqnsLhi8BmX-QP3WVheE3d4mScAAwqrw@z> On Thu, Apr 18, 2019 at 04:30:48PM +0200, Greg Kroah-Hartman wrote: > On Thu, Apr 18, 2019 at 10:21:32AM -0400, Alan Stern wrote: > > On Thu, 18 Apr 2019, Greg Kroah-Hartman wrote: > > > > > On Wed, Apr 17, 2019 at 04:20:09PM -0700, Guenter Roeck wrote: > > > > On Wed, Apr 17, 2019 at 3:41 PM Raul Rangel wrote: > > > > > > > > > > On Wed, Apr 17, 2019 at 03:23:52PM -0700, Guenter Roeck wrote: > > > > > > On Wed, Apr 17, 2019 at 3:11 PM Raul Rangel wrote: > > > > > > > > > > > > > > On Wed, Apr 17, 2019 at 04:39:23PM -0400, Alan Stern wrote: > > > > > > > > > > > > > > > > This sounds like a golden opportunity! Submit a separate patch making > > > > > > > > the parameter to kobject_uevent_env be const (actually const char * > > > > > > > > const []), then submit this patch on top of that one. > > > > > > > So there are other parts of the code base that dynamically create their > > > > > > > array values. So by making the function take const, it breaks :( > > > > > > > > > > > > Confused. The calling code can still be non-const. I don't see the > > > > > > parameter modified in kobject_uevent_env(), so declaring it const > > > > > > should be possible. Can you give an example of code that no longer > > > > > > works ? > > > > > static int notify_user_space(struct thermal_zone_device *tz, int trip) > > > > > { > > > > > char *thermal_prop[5]; > > > > > int i; > > > > > > > > > > mutex_lock(&tz->lock); > > > > > thermal_prop[0] = kasprintf(GFP_KERNEL, "NAME=%s", tz->type); > > > > > thermal_prop[1] = kasprintf(GFP_KERNEL, "TEMP=%d", tz->temperature); > > > > > thermal_prop[2] = kasprintf(GFP_KERNEL, "TRIP=%d", trip); > > > > > thermal_prop[3] = kasprintf(GFP_KERNEL, "EVENT=%d", tz->notify_event); > > > > > thermal_prop[4] = NULL; > > > > > kobject_uevent_env(&tz->device.kobj, KOBJ_CHANGE, thermal_prop); > > > > > for (i = 0; i < 4; ++i) > > > > > kfree(thermal_prop[i]); > > > > > mutex_unlock(&tz->lock); > > > > > return 0; > > > > > } > > > > > > > > > > drivers/thermal/user_space.c:48:52: error: passing 'char *[5]' to parameter of type 'const char *const *' discards qualifiers in nested pointer types [-Werror,-Wincompatible-pointer-types-discards-qualifiers] > > > > > kobject_uevent_env(&tz->device.kobj, KOBJ_CHANGE, thermal_prop); > > > > > ^~~~~~~~~~~~ > > > > > include/linux/kobject.h:238:22: note: passing argument to parameter 'envp' here > > > > > const char *const envp[]); > > > > > ^ > > > > > > > > > > http://c-faq.com/ansi/constmismatch.html explains why it fails. > > > > > > > > > Interesting. One never stops learning. So the best you could do would > > > > be char * const envp[], but I guess that doesn't help much. > > > > > > Yeah, I went down this path a year or so ago and had to give it up as > > > well :( > > > > Well, the signature could still be changed as Guenter suggests. > > > > And the array being added in the new code could still be static. > > After all, there isn't really any danger that the contents of those > > strings will be modified, right? It's just that the const modifiers > > weren't put in until it was too late and there were too many existing > > callers. Perhaps a comment about this could be included in the > > kerneldoc for kobject_uevent_env. > > I am all for changing this, but I remember I tried to, and somehow > failed, but I don't remember the full details sorry, it was a while ago. > If someone figures out how to make this all const, I will gladly take > that patch. > Well we could use varargs... int kobject_uevent_env(struct kobject *kobj, enum kobject_action action, ...); This will accept both const char* and char *. Example https://repl.it/@RaulRangel/Const-char-var-args It seems like most callers have a fixed number of env params, so you wouldn't need a function that takes a list. > thanks, > > greg k-h