Re: [PATCH v4] char: xillybus: Fix error handling in xillybus_init_chrdev()

[Eli Billauer]

Hello,

On 19/07/2025 15:17, Ma Ke wrote:
> Use cdev_del() instead of direct kobject_put() when cdev_add() fails.
> This aligns with standard kernel practice and maintains consistency
> within the driver's own error paths.
Sorry, to the extent it matters, I'm not acknowledging this.

This is merely a code styling issue, and as far as I know, there is no 
"standard kernel practice" on this matter. If such standard practice 
exists, the correct way is to prepare a patchset of *all* occurrences of 
kobject_put() used this way, and replace them all (e.g. fs/char_dev.c, 
uio/uio.c and tty/tty_io.c). Should xillybus_class be included in this 
patchset, I will of course ack it, not that it would matter much.

In my opinion, using cdev_del() is incorrect, as you can't delete 
something that failed to be added. Practically this causes no problem, 
but as a question of style, the kobject_put() call acts as the reversal 
of cdev_alloc(). This is formally more accurate, and this is the reason 
I chose to do it this way.

But more than anything, I find this patch pointless, unless someone 
explains why it has any use. I'm open to new insights.

Regards,
   Eli