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[104.188.17.28]) by smtp.gmail.com with ESMTPSA id z25sm21277934pfg.140.2020.07.21.13.58.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 21 Jul 2020 13:58:29 -0700 (PDT) Date: Tue, 21 Jul 2020 13:56:35 -0700 From: Bjorn Andersson To: Siddharth Gupta Cc: Mathieu Poirier , agross@kernel.org, ohad@wizery.com, corbet@lwn.net, linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, tsoni@codeaurora.org, psodagud@codeaurora.org, rishabhb@codeaurora.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v4 1/2] remoteproc: Add remoteproc character device interface Message-ID: <20200721205635.GM2922385@builder.lan> References: <1594148870-27276-1-git-send-email-sidgup@codeaurora.org> <1594148870-27276-2-git-send-email-sidgup@codeaurora.org> <20200715201839.GA3204081@xps15> <20200715215149.GA3267350@xps15> <81d7514c-727e-b4dc-e4ac-74a25966ccaf@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <81d7514c-727e-b4dc-e4ac-74a25966ccaf@codeaurora.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 21 Jul 12:16 PDT 2020, Siddharth Gupta wrote: > On 7/15/2020 2:51 PM, Mathieu Poirier wrote: > > On Wed, Jul 15, 2020 at 02:18:39PM -0600, Mathieu Poirier wrote: > > > On Tue, Jul 07, 2020 at 12:07:49PM -0700, Siddharth Gupta wrote: [..] > > > > diff --git a/drivers/remoteproc/remoteproc_cdev.c b/drivers/remoteproc/remoteproc_cdev.c [..] > > > > +int rproc_char_device_add(struct rproc *rproc) > > > > +{ > > > > + int ret; > > > > + dev_t cdevt; > > > > + > > > > + cdev_init(&rproc->char_dev, &rproc_fops); > > > > + rproc->char_dev.owner = THIS_MODULE; > > > > + > > > > + cdevt = MKDEV(rproc_major, rproc->index); > > > > + ret = cdev_add(&rproc->char_dev, cdevt, 1); > > Trying this patchset on my side gave me the following splat[1]. After finding > > the root case I can't understand how you haven't see it on your side when you > > tested the feature. > > > > [1]. https://pastebin.com/aYTUUCdQ Mathieu, I've looked at this back and forth. Afaict this implies that rproc_major is still 0. Could it be that either alloc_chrdev_region() failed or somehow has yet to be called when you hit this point? > Hey Mathieu, > > We aren't able to reproduce the error that you are seeing, the splat is > coming > from the check for whiteout device[1] - which shouldn't happen because of > the > find_dynamic_major call[2], right? > > We are successfully seeing all our character device files and able to > successfully boot remoteprocs. From what I read and understood about > whiteout > devices they will be hidden in the fs. > > Could you provide more details about your configuration and testing? > > [1]: https://github.com/torvalds/linux/blob/master/fs/char_dev.c#L486 > > [2]: https://github.com/torvalds/linux/blob/master/fs/char_dev.c#L123 > > > > > > + if (ret < 0) > > > > + goto out; > > > > + > > > > + rproc->dev.devt = cdevt; > > > > +out: > > > > + return ret; > > > > +} > > > > + > > > > +void rproc_char_device_remove(struct rproc *rproc) > > > > +{ > > > > + __unregister_chrdev(rproc_major, rproc->index, 1, "remoteproc"); > > > > +} > > > > + > > > > +void __init rproc_init_cdev(void) > > > > +{ > > > > + int ret; > > > > + > > > > + ret = alloc_chrdev_region(&rproc_major, 0, NUM_RPROC_DEVICES, "remoteproc"); > > > > + if (ret < 0) > > > > + pr_err("Failed to alloc rproc_cdev region, err %d\n", ret); > > > > +} > > > > + > > > > +void __exit rproc_exit_cdev(void) > > > > +{ > > > > + unregister_chrdev_region(MKDEV(rproc_major, 0), NUM_RPROC_DEVICES); > > > Please go back to the comment I made on this during my last review and respin. > > After digging in the code while debugging the above problem, I don't see how > > unregistering the chrdev region the way it is done here would have worked. > Since this is compiled statically and not built as a module, we will never > exercise the code path, so I will remove it in the next patchset. > You're right Siddharth, since we changed CONFIG_REMOTEPROC to bool it's no longer possible to hit remoteproc_exit(), so you can omit this function entirely. (And we should clean up the rest of that as well) [..] > > > > diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h [..] > > > > @@ -488,6 +489,8 @@ struct rproc_dump_segment { > > > > * @auto_boot: flag to indicate if remote processor should be auto-started > > > > * @dump_segments: list of segments in the firmware > > > > * @nb_vdev: number of vdev currently handled by rproc > > > > + * @char_dev: character device of the rproc > > > > + * @cdev_put_on_release: flag to indicate if remoteproc should be shutdown on @char_dev release > > > > */ > > > > struct rproc { > > > > struct list_head node; > > > > @@ -523,6 +526,8 @@ struct rproc { > > > > int nb_vdev; > > > > u8 elf_class; > > > > u16 elf_machine; > > > > + struct cdev char_dev; As stated privately, I assumed based on this name that this is a struct device related to that character device. So please rename this cdev to save me from doing this mistake again. Thanks, Bjorn