linux-kernel - [RFC PATCH v2 2/2] staging: media: atomisp: Simplify logic in vmem.c

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Message-ID: <20250903092754.2751556-3-abarnas@google.com>
Date: Wed,  3 Sep 2025 09:27:54 +0000
From: "Adrian Barnaś" <abarnas@...gle.com>
To: Hans de Goede <hansg@...nel.org>, Mauro Carvalho Chehab <mchehab@...nel.org>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, Andy Shevchenko <andy@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Dan Carpenter <dan.carpenter@...aro.org>, 
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-staging@...ts.linux.dev
Cc: "Adrian Barnaś" <abarnas@...gle.com>
Subject: [RFC PATCH v2 2/2] staging: media: atomisp: Simplify logic in vmem.c

Add inline helper and simplify logic for subword operations in
pci/hive_isp_css_common/host/vmem.c.

Signed-off-by: Adrian Barnaś <abarnas@...gle.com>
---
 .../media/atomisp/pci/hive_isp_css_common/host/vmem.c    | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/staging/media/atomisp/pci/hive_isp_css_common/host/vmem.c b/drivers/staging/media/atomisp/pci/hive_isp_css_common/host/vmem.c
index a3fe03216389..f11b0448ed83 100644
--- a/drivers/staging/media/atomisp/pci/hive_isp_css_common/host/vmem.c
+++ b/drivers/staging/media/atomisp/pci/hive_isp_css_common/host/vmem.c
@@ -15,18 +15,23 @@
 
 /* Copied from SDK: sim_semantics.c */
 
+static inline unsigned long long subword_bitmask(unsigned int start, unsigned int end)
+{
+	return GENMASK_ULL(end - 1, 0) & ~(GENMASK_ULL(start, 0) >> 1);
+}
+
 /* subword bits move like this:         MSB[____xxxx____]LSB -> MSB[00000000xxxx]LSB */
 static inline unsigned long long
 subword(unsigned long long w, unsigned int start, unsigned int end)
 {
-	return (w & (((1ULL << (end - 1)) - 1) << 1 | 1)) >> start;
+	return (w & GENMASK_ULL(end - 1, 0)) >> start;
 }
 
 /* clears subword bits like this: MSB[xxxx____xxxx]LSB -> MSB[xxxx0000xxxx]LSB */
 static inline unsigned long long
 clear_subword(unsigned long long w, unsigned int start, unsigned int end)
 {
-	return w & (~(((1ULL << (end - 1)) - 1) << 1 | 1) | ((1ULL << start) - 1));
+	return w & ~subword_bitmask(start, end);
 }
 
 #define uedge_bits (8 * sizeof(unsigned long long))
-- 
2.51.0.355.g5224444f11-goog