On Tue, Feb 06, 2024 at 11:26 AM +0800, Guenter Roeck wrote: > > On 2/5/24 19:05, Cosmo Chou wrote: > > On Tue, Feb 06, 2024 at 3:43 AM +0800, Guenter Roeck wrote: > >> > >> On Mon, Feb 05, 2024 at 11:20:13PM +0800, Cosmo Chou wrote: > >>> This driver implements support for temperature monitoring of Astera Labs > >>> PT5161L series PCIe retimer chips. > >>> > >>> This driver implementation originates from the CSDK available at > >>> Link: https://github.com/facebook/openbmc/tree/helium/common/recipes-lib/retimer-v2.14 > >>> The communication protocol utilized is based on the I2C/SMBus standard. > >>> > >>> Signed-off-by: Cosmo Chou <chou.cosmo@xxxxxxxxx> > >>> --- > >> [ ... ] > >> > >>> +static ssize_t pt5161l_debugfs_read_fw_ver(struct file *file, char __user *buf, > >>> + size_t count, loff_t *ppos) > >>> +{ > >>> + struct pt5161l_data *data = file->private_data; > >>> + int ret; > >>> + char ver[32]; > >>> + > >>> + mutex_lock(&data->lock); > >>> + ret = pt5161l_fwsts_check(data); > >>> + mutex_unlock(&data->lock); > >>> + if (ret) > >>> + return ret; > >>> + > >>> + ret = snprintf(ver, sizeof(ver), "%u.%u.%u\n", data->fw_ver.major, > >>> + data->fw_ver.minor, data->fw_ver.build); > >>> + if (ret < 0) > >>> + return ret; > >>> + > >> > >> You almost got me here ;-). snprintf() never returns a negative error code, > >> so checking for it is not necessary. > >> > > Oh! You're right. > > > >>> + return simple_read_from_buffer(buf, count, ppos, ver, ret + 1); > >> > >> Number of bytes written plus 1 ? Why ? > > It's just to include the string terminator '\0'. > > > > If that was needed, it would be risky. snprintf() truncates the output > if the buffer is not large enough. You might want to consider using > scnprintf() instead. But then I am not sure if that is needed in the first > place. Almost all code I checked doesn't do that, and it seems to be likely > that the few drivers who do that are simply wrong. Can you explain why the > string terminator needs to be added to the output ? > > Thanks, > Guenter > It's just in case someone reads and prints this, but with a dirty buffer and doesn't handle the terminator.
