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

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Date:   Thu, 18 Feb 2021 10:31:15 +0000
From:   Ian Abbott <abbotti@....co.uk>
To:     Atul Gopinathan <atulgopinathan@...il.com>,
        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 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.

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=9d5d041eebe3dcf7591ff7004896c329eb841ca6

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