[PATCHi v3] staging: rts5208: Convert kmap() to kmap_local_page()

[PATCHi v3] staging: rts5208: Convert kmap() to kmap_local_page()

[Fabio M. De Francesco]

The use of kmap() is being deprecated in favor of kmap_local_page()
where it is feasible.

With kmap_local_page(), the mapping is per thread, CPU local and not
globally visible. Therefore rtsx_stor_access_xfer_buf() is a function
where the use of kmap_local_page() in place of kmap() is correctly
suited.

Convert to kmap_local_page() but, instead of open coding it, use the
helpers memcpy_to_page() and memcpy_from_page().

Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
---

v1 -> v2: Rework the commit message and use the appropriate helpers
instead of open coding the use of kmap_local_page()/kunmap_local_page().
(Thanks to Ira Weiny <ira.weiny@intel.com>).

v2 -> v3: Use memcpy_{to,from}_page() arguments correctly.
(Thanks to Dan Carpenter <dan.carpenter@oracle.com>).

 drivers/staging/rts5208/rtsx_transport.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/staging/rts5208/rtsx_transport.c b/drivers/staging/rts5208/rtsx_transport.c
index 805dc18fac0a..b702c7caf944 100644
--- a/drivers/staging/rts5208/rtsx_transport.c
+++ b/drivers/staging/rts5208/rtsx_transport.c
@@ -92,13 +92,11 @@ unsigned int rtsx_stor_access_xfer_buf(unsigned char *buffer,
 			while (sglen > 0) {
 				unsigned int plen = min(sglen, (unsigned int)
 						PAGE_SIZE - poff);
-				unsigned char *ptr = kmap(page);
 
 				if (dir == TO_XFER_BUF)
-					memcpy(ptr + poff, buffer + cnt, plen);
+					memcpy_to_page(page, poff, buffer + cnt, plen);
 				else
-					memcpy(buffer + cnt, ptr + poff, plen);
-				kunmap(page);
+					memcpy_from_page(buffer + cnt, page, poff, plen);
 
 				/* Start at the beginning of the next page */
 				poff = 0;
-- 
2.34.1

Re: [PATCHi v3] staging: rts5208: Convert kmap() to kmap_local_page()

[Ira Weiny]

On Tue, Mar 29, 2022 at 06:20:55PM +0200, Fabio M. De Francesco wrote:
> The use of kmap() is being deprecated in favor of kmap_local_page()
> where it is feasible.
> 
> With kmap_local_page(), the mapping is per thread, CPU local and not
> globally visible. Therefore rtsx_stor_access_xfer_buf() is a function
> where the use of kmap_local_page() in place of kmap() is correctly
> suited.
> 
> Convert to kmap_local_page() but, instead of open coding it, use the
> helpers memcpy_to_page() and memcpy_from_page().
> 
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
> ---
> 
> v1 -> v2: Rework the commit message and use the appropriate helpers
> instead of open coding the use of kmap_local_page()/kunmap_local_page().
> (Thanks to Ira Weiny <ira.weiny@intel.com>).
> 
> v2 -> v3: Use memcpy_{to,from}_page() arguments correctly.
> (Thanks to Dan Carpenter <dan.carpenter@oracle.com>).
> 
>  drivers/staging/rts5208/rtsx_transport.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/rts5208/rtsx_transport.c b/drivers/staging/rts5208/rtsx_transport.c
> index 805dc18fac0a..b702c7caf944 100644
> --- a/drivers/staging/rts5208/rtsx_transport.c
> +++ b/drivers/staging/rts5208/rtsx_transport.c
> @@ -92,13 +92,11 @@ unsigned int rtsx_stor_access_xfer_buf(unsigned char *buffer,
>  			while (sglen > 0) {
>  				unsigned int plen = min(sglen, (unsigned int)
>  						PAGE_SIZE - poff);
> -				unsigned char *ptr = kmap(page);
>  
>  				if (dir == TO_XFER_BUF)
> -					memcpy(ptr + poff, buffer + cnt, plen);
> +					memcpy_to_page(page, poff, buffer + cnt, plen);
>  				else
> -					memcpy(buffer + cnt, ptr + poff, plen);
> -				kunmap(page);
> +					memcpy_from_page(buffer + cnt, page, poff, plen);

This code is great...  But I went and looked at the function and found a
comment which needs to be updated as well.  :-/

 57         /*
 58          * Using scatter-gather.  We have to go through the list one entry
 59          * at a time.  Each s-g entry contains some number of pages, and
 60          * each page has to be kmap()'ed separately.
 61          */

I would update it to say something like:

...  Each s-g entry contains some number of pages which have to be copied one
at a time.

Sorry for not catching that earlier,
Ira

>  
>  				/* Start at the beginning of the next page */
>  				poff = 0;
> -- 
> 2.34.1
>