linux-kernel - Re: [PATCH v2] debugfs: allow to use regmap for print regs

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Message-ID: <Y76UBsukAz+yQ9bW@kroah.com>
Date:   Wed, 11 Jan 2023 11:48:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Li Chen <me@...ux.beauty>
Cc:     "rafael j. wysocki" <rafael@...nel.org>,
        li chen <lchen@...arella.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] debugfs: allow to use regmap for print regs

On Wed, Jan 11, 2023 at 04:27:20PM +0800, Li Chen wrote:
> Hi Greg,
>  ---- On Wed, 11 Jan 2023 15:42:44 +0800  Greg Kroah-Hartman  wrote --- 
>  > On Wed, Jan 11, 2023 at 03:21:29PM +0800, Li Chen wrote:
>  > > From: Li Chen lchen@...arella.com>
>  > > 
>  > > Currently, debugfs_regset32 only contains void __iomem *base,
>  > > and it is not friendly to regmap user.
>  > > 
>  > > Let's add regmap to debugfs_regset32, and add debugfs_print_regmap_reg32
>  > > to allow debugfs_regset32_show handle regmap.
>  > > 
>  > > Signed-off-by: Li Chen lchen@...arella.com>
>  > 
>  > Do you have an actual in-kernel user for this new function?  We can't
>  > accept new apis without users for obvious reasaons.
> 
> Actually, both the old debugfs_print_regs32 and the new debugfs_regmap_print_regs32
> have only one user: debugfs_regset32_show located inside debugfs/file.c.

Yes, but that function is used by lots of drivers in the kernel today,
which is fine.

> The difference is currently all users(device drivers) only use debugfs_regset32->base,
> and none of them use debugfs_regset32->regmap, which is provided by this patch.
> 
> I'm not sure whether it violates the kernel's "no user, no new function" ruler or not.

Yes, you would have to have a user for this functionality for us to be
able to take the change.

> I use this regmap locally on our SoC driver, but it is still not ready to upstream, really sorry for it,
> and it is not a good idea to change existing non-regmap users to regmap haha.
>  
> If you think it does matter, please tell me and I will upload v3 with our SoC driver in the future.

Please add it to your SoC driver patch series instead and I will be glad
to review it at that point in time.  But for now, this shouldn't be
needed.

thanks,

greg k-h