linux-kernel - [PATCH V2 linux-next] staging: media: atomisp: kmap() can't fail

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Message-Id: <20170426184423.21301-1-fabf@skynet.be>
Date:   Wed, 26 Apr 2017 20:44:23 +0200
From:   Fabian Frederick <fabf@...net.be>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Cox <alan@...ux.intel.com>
Cc:     Jan Kara <jack@...e.com>, linux-kernel@...r.kernel.org,
        fabf@...net.be
Subject: [PATCH V2 linux-next] staging: media: atomisp: kmap() can't fail

There's no need to check kmap() return value because it won't fail.
If it's highmem mapping, it will receive virtual address
or a new one; if it's lowmem, all kernel pages are already being mapped.

(Thanks to Jan Kara for explanations)

Signed-off-by: Fabian Frederick <fabf@...net.be>
---
V2: Verbose description (suggested by Greg Kroah-Hartman)

 drivers/staging/media/atomisp/pci/atomisp2/hmm/hmm.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/drivers/staging/media/atomisp/pci/atomisp2/hmm/hmm.c b/drivers/staging/media/atomisp/pci/atomisp2/hmm/hmm.c
index 151abf0..7d2f8d9 100644
--- a/drivers/staging/media/atomisp/pci/atomisp2/hmm/hmm.c
+++ b/drivers/staging/media/atomisp/pci/atomisp2/hmm/hmm.c
@@ -328,15 +328,7 @@ static int load_and_flush_by_kmap(ia_css_ptr virt, void *data, unsigned int byte
 		idx = (virt - bo->start) >> PAGE_SHIFT;
 		offset = (virt - bo->start) - (idx << PAGE_SHIFT);
 
-		src = (char *)kmap(bo->page_obj[idx].page);
-		if (!src) {
-			dev_err(atomisp_dev,
-				    "kmap buffer object page failed: "
-				    "pg_idx = %d\n", idx);
-			return -EINVAL;
-		}
-
-		src += offset;
+		src = (char *)kmap(bo->page_obj[idx].page) + offset;
 
 		if ((bytes + offset) >= PAGE_SIZE) {
 			len = PAGE_SIZE - offset;
@@ -533,14 +525,7 @@ int hmm_set(ia_css_ptr virt, int c, unsigned int bytes)
 		idx = (virt - bo->start) >> PAGE_SHIFT;
 		offset = (virt - bo->start) - (idx << PAGE_SHIFT);
 
-		des = (char *)kmap(bo->page_obj[idx].page);
-		if (!des) {
-			dev_err(atomisp_dev,
-				    "kmap buffer object page failed: "
-				    "pg_idx = %d\n", idx);
-			return -EINVAL;
-		}
-		des += offset;
+		des = (char *)kmap(bo->page_obj[idx].page) + offset;
 
 		if ((bytes + offset) >= PAGE_SIZE) {
 			len = PAGE_SIZE - offset;
-- 
2.9.3