linux-kernel - Re: [PATCH v4 1/5] vfio/migration: Add debugfs to live migration driver

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Message-ID: <Y434Pivb5PwzP0TI@nvidia.com>
Date:   Mon, 5 Dec 2022 09:55:10 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     liulongfang <liulongfang@...wei.com>
Cc:     alex.williamson@...hat.com, shameerali.kolothum.thodi@...wei.com,
        john.garry@...wei.com, cohuck@...hat.com,
        linux-kernel@...r.kernel.org, linuxarm@...neuler.org
Subject: Re: [PATCH v4 1/5] vfio/migration: Add debugfs to live migration
 driver

On Mon, Dec 05, 2022 at 09:39:29PM +0800, liulongfang wrote:
> On 2022/12/2 23:17, Jason Gunthorpe wrote:
> > On Fri, Dec 02, 2022 at 05:26:21PM +0800, Longfang Liu wrote:
> > 
> >> +static ssize_t vfio_pci_vf_state_read(struct file *filp, char __user *buffer,
> >> +			   size_t count, loff_t *pos)
> >> +{
> > 
> > This would be better to use debugfs_create_devm_seqfile()
> > 
> > Then you can simply use seq_printf()
> >
> 
> The previous debugfs used this method in my patch.
> Is it now recommended to use the interface with "devm" ?

It doesn't matter, the point is not the devm, it is to use the right
helper for the data you want to expose over debugfs 
 
> >> @@ -119,6 +129,8 @@ struct vfio_migration_ops {
> >>  				   enum vfio_device_mig_state *curr_state);
> >>  	int (*migration_get_data_size)(struct vfio_device *device,
> >>  				       unsigned long *stop_copy_length);
> >> +	int (*migration_get_data)(struct vfio_device *device, char *buffer);
> >> +	int (*migration_get_attr)(struct vfio_device *device, char
> >>  				   *buffer);
> > 
> > Still no to passing through debugfs ops, create these files in the
> > driver.
> > 
> 
> If this part is also created and enabled in the device driver, why do we need
> to put this debugfs in the vfio public framework?

To create the directory, and the few actually common files

Jason