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Sat, 7 Feb 2026 10:55:16 -0500 (EST) Date: Sat, 7 Feb 2026 16:55:14 +0100 From: Greg KH To: Viacheslav Dubeyko Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, bpf@vger.kernel.org, Slava.Dubeyko@ibm.com, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v1 3/4] ml-lib: Implement simple testing character device driver Message-ID: <2026020719-thrive-domain-f0c2@gregkh> References: <20260206191136.2609767-1-slava@dubeyko.com> <20260206191136.2609767-4-slava@dubeyko.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260206191136.2609767-4-slava@dubeyko.com> X-Stat-Signature: 17pxy8ut1m96hqpccb78gdxk3i41xna6 X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 3979110000F X-HE-Tag: 1770479719-1785 X-HE-Meta: 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 A/Km39v/ mdjq+ X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Feb 06, 2026 at 11:11:35AM -0800, Viacheslav Dubeyko wrote: > Implement simple testing character device driver > > Signed-off-by: Viacheslav Dubeyko It's hard to tell if this is just an early april-fools joke or not, but if it's not: > +### Character Device Operations > +- **Open/Close**: Device can be opened and closed multiple times > +- **Read**: Read data from a kernel buffer > +- **Write**: Write data to a kernel buffer (1KB capacity) > +- **Seek**: Support for lseek() operations > + > +### IOCTL Commands > +- `ML_LIB_TEST_DEV_IOCRESET`: Clear the device buffer > +- `ML_LIB_TEST_DEV_IOCGETSIZE`: Get current data size > +- `ML_LIB_TEST_DEV_IOCSETSIZE`: Set data size > + > +### Sysfs Attributes > +Located at `/sys/class/ml_lib_test/mllibdev`: > +- `buffer_size`: Maximum buffer capacity (read-only) > +- `data_size`: Current amount of data in buffer (read-only) > +- `access_count`: Number of times device has been opened (read-only) > +- `stats`: Comprehensive statistics (opens, reads, writes) Again, this is not an acceptable use of sysfs. > + /* Allocate device number */ > + ret = alloc_chrdev_region(&dev_number, 0, 1, DEVICE_NAME); Don't burn a cdev for this, please use the misc device api. good luck! greg k-h