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Thu, 10 Oct 2024 03:54:13 -0400 (EDT) Date: Thu, 10 Oct 2024 09:54:11 +0200 From: Greg KH To: Rodolfo Giometti Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, Andrew Morton , corbet@lwn.net, Hall Christopher S , Mohan Subramanian , tglx@linutronix.de, andriy.shevchenko@linux.intel.com, Dong Eddie , N Pandith , T R Thejesh Reddy , Zage David , Chinnadurai Srinivasan Subject: Re: [RFC 1/3] drivers pps: add PPS generators support Message-ID: <2024101002-viscous-egomaniac-04d3@gregkh> References: <20241008135033.3171915-1-giometti@enneenne.com> <20241008135033.3171915-2-giometti@enneenne.com> <2024100855-unsecured-mammogram-001a@gregkh> <541eb5c6-5546-4170-9e8b-d421d55822a1@enneenne.com> <2024101013-reputably-skid-9e01@gregkh> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, Oct 10, 2024 at 09:32:22AM +0200, Rodolfo Giometti wrote: > On 10/10/24 09:15, Greg KH wrote: > > On Wed, Oct 09, 2024 at 10:48:14AM +0200, Rodolfo Giometti wrote: > > > > > +#ifdef CONFIG_COMPAT > > > > > +static long pps_gen_cdev_compat_ioctl(struct file *file, > > > > > + unsigned int cmd, unsigned long arg) > > > > > +{ > > > > > + cmd = _IOC(_IOC_DIR(cmd), _IOC_TYPE(cmd), _IOC_NR(cmd), sizeof(void *)); > > > > > + return pps_gen_cdev_ioctl(file, cmd, arg); > > > > > +} > > > > > +#else > > > > > +#define pps_gen_cdev_compat_ioctl NULL > > > > > +#endif > > > > > + > > > > > +static struct pps_gen_device *pps_gen_idr_get(unsigned long id) > > > > > +{ > > > > > + struct pps_gen_device *pps_gen; > > > > > + > > > > > + mutex_lock(&pps_gen_idr_lock); > > > > > + pps_gen = idr_find(&pps_gen_idr, id); > > > > > + if (pps_gen) > > > > > + kobject_get(&pps_gen->dev->kobj); > > > > > + > > > > > + mutex_unlock(&pps_gen_idr_lock); > > > > > > > > Doesn't an idr have a lock in it? I can never remember... > > > > > > As far as I know we must use a mutex... > > > > If you do, someone will come along and remove it, please see: > > https://lore.kernel.org/r/b1fcc6707ec2b6309d50060fa52ccc2c892afde2.1728507153.git.christophe.jaillet@wanadoo.fr > > as an example (with links that show it is not needed). > > Here is an example about ida API, but I'm using idr API. Why not use ida then? :)