linux-kernel - Re: [PATCH V3 02/21] dax: add fsdev.c driver for fs-dax on character dax

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Message-ID: <aWA80edCywOLw0li@gourry-fedora-PF4VCD3F>
Date: Thu, 8 Jan 2026 18:25:05 -0500
From: Gregory Price <gourry@...rry.net>
To: John Groves <John@...ves.net>
Cc: Jonathan Cameron <jonathan.cameron@...wei.com>,
	Miklos Szeredi <miklos@...redi.hu>,
	Dan Williams <dan.j.williams@...el.com>,
	Bernd Schubert <bschubert@....com>,
	Alison Schofield <alison.schofield@...el.com>,
	John Groves <jgroves@...ron.com>, Jonathan Corbet <corbet@....net>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.cz>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	David Hildenbrand <david@...nel.org>,
	Christian Brauner <brauner@...nel.org>,
	"Darrick J . Wong" <djwong@...nel.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Jeff Layton <jlayton@...nel.org>,
	Amir Goldstein <amir73il@...il.com>,
	Stefan Hajnoczi <shajnocz@...hat.com>,
	Joanne Koong <joannelkoong@...il.com>,
	Josef Bacik <josef@...icpanda.com>,
	Bagas Sanjaya <bagasdotme@...il.com>,
	Chen Linxuan <chenlinxuan@...ontech.com>,
	James Morse <james.morse@....com>, Fuad Tabba <tabba@...gle.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Shivank Garg <shivankg@....com>,
	Ackerley Tng <ackerleytng@...gle.com>,
	Aravind Ramesh <arramesh@...ron.com>,
	Ajay Joshi <ajayjoshi@...ron.com>, venkataravis@...ron.com,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
	nvdimm@...ts.linux.dev, linux-cxl@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH V3 02/21] dax: add fsdev.c driver for fs-dax on character
 dax

On Thu, Jan 08, 2026 at 03:15:10PM -0600, John Groves wrote:
> On 26/01/08 09:12AM, John Groves wrote:
> > On 26/01/08 11:31AM, Jonathan Cameron wrote:
> > > On Wed,  7 Jan 2026 09:33:11 -0600
> > > John Groves <John@...ves.net> wrote:
> 
> [ ... ]
> 
> > > > diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
> > > > index d656e4c0eb84..491325d914a8 100644
> > > > --- a/drivers/dax/Kconfig
> > > > +++ b/drivers/dax/Kconfig
> > > > @@ -78,4 +78,21 @@ config DEV_DAX_KMEM
> > > >  
> > > >  	  Say N if unsure.
> > > >  
> > > > +config DEV_DAX_FS
> > > > +	tristate "FSDEV DAX: fs-dax compatible device driver"
> > > > +	depends on DEV_DAX
> > > > +	default DEV_DAX
> > > 
> > > What's the logic for the default? Generally I'd not expect a
> > > default for something new like this (so default of default == no)
> > 
> > My thinking is that this is harmless unless you use it, but if you
> > need it you need it. So defaulting to include the module seems
> > viable.
> > 
> > [ ... ]
> 
> On further deliberation, I think I'd like to get rid of 
> CONFIG_DEV_DAX_FS, and just include the fsdev_dax driver if DEV_DAX
> and FS_DAX are configured. Then CONFIG_FUSE_FAMFS_DAX (controlling the
> famfs code in fuse) can just depend on DEV_DAX, FS_DAX and FUSE_FS. 
> 
> That's where I'm leaning for the next rev of the series...
> 
> John
>

Please do that for CXL_DAX or whatever because it's really annoying to
have CXL and DAX configured but not have your dax device show up because
CXL_DAX wasn't configured.

:P

~Gregory