linux-kernel - Re: [PATCH v2 1/2] staging: comedi: cast function output to assigned variable type

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Message-ID: <20210218104755.GA7571@atulu-nitro>
Date:   Thu, 18 Feb 2021 16:17:55 +0530
From:   Atul Gopinathan <atulgopinathan@...il.com>
To:     Ian Abbott <abbotti@....co.uk>, gregkh@...uxfoundation.org
Cc:     hsweeten@...ionengravers.com, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] staging: comedi: cast function output to assigned
 variable type

On Thu, Feb 18, 2021 at 10:31:15AM +0000, Ian Abbott wrote:
> On 18/02/2021 08:44, Atul Gopinathan wrote:
> > Fix the following warning generated by sparse:
> > 
> > drivers/staging//comedi/comedi_fops.c:2956:23: warning: incorrect type in assignment (different address spaces)
> > drivers/staging//comedi/comedi_fops.c:2956:23:    expected unsigned int *chanlist
> > drivers/staging//comedi/comedi_fops.c:2956:23:    got void [noderef] <asn:1> *
> > 
> > compat_ptr() has a return type of "void __user *"
> > as defined in "include/linux/compat.h"
> > 
> > cmd->chanlist is of type "unsigned int *" as defined
> > in drivers/staging/comedi/comedi.h" in struct
> > comedi_cmd.
> > 
> > Signed-off-by: Atul Gopinathan <atulgopinathan@...il.com>
> > ---
> >   drivers/staging/comedi/comedi_fops.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
> > index e85a99b68f31..fc4ec38012b4 100644
> > --- a/drivers/staging/comedi/comedi_fops.c
> > +++ b/drivers/staging/comedi/comedi_fops.c
> > @@ -2953,7 +2953,7 @@ static int get_compat_cmd(struct comedi_cmd *cmd,
> >   	cmd->scan_end_arg = v32.scan_end_arg;
> >   	cmd->stop_src = v32.stop_src;
> >   	cmd->stop_arg = v32.stop_arg;
> > -	cmd->chanlist = compat_ptr(v32.chanlist);
> > +	cmd->chanlist = (unsigned int __force *)compat_ptr(v32.chanlist);
> >   	cmd->chanlist_len = v32.chanlist_len;
> >   	cmd->data = compat_ptr(v32.data);
> >   	cmd->data_len = v32.data_len;
> > 
> 
> This patch and the other one in your series clash with commit 9d5d041eebe3
> ("staging: comedi: comedi_fops.c: added casts to get rid of sparse
> warnings") by B K Karthik.

Oh I see. Not sure if this is the right place to ask, but which tree and
branch should one work with when messing with the code in staging/
directory? (wanted to avoid such clashes in future)

Thanks,
Atul