This is a note to let you know that I've just added the patch titled
ihex: Simplify next record offset calculation
to my driver-core git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
in the driver-core-testing branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will be merged to the driver-core-next branch sometime soon,
after it passes testing, and the merge window is open.
If you have any questions about this process, please let me know.
>From 9fb4ab4d3dd665a62da9c176a89e7c7feaf5d9e4 Mon Sep 17 00:00:00 2001
From: Andrey Smirnov <andrew.smir...@gmail.com>
Date: Thu, 20 Dec 2018 23:28:39 -0800
Subject: ihex: Simplify next record offset calculation
Next record calucaltion can be reduced to a much more tivial ALIGN
operation as follows:
1. Splitting 5 into 2 + 3 we get
next = ((be16_to_cpu(rec->len) + 2 + 3) & ~3) - 2 (1)
2. Using ALIGN macro we reduce (1) to:
ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2 (2)
3. Subsituting 'next' in original next record calucation we get:
(void *)&rec->data[ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2] (3)
4. Converting array index to pointer arithmetic we convert (3) into:
(void *)rec + sizeof(*rec) +
ALIGN(be16_to_cpu(rec->len) + 2, 4) - 2 (4)
5. Subsituting sizeof(*rec) with its value, 6, and substracting 2,
in (4) we get:
(void *)rec + ALIGN(be16_to_cpu(rec->len) + 2, 4) + 4 (5)
6. Since ALIGN(X, 4) + 4 == ALIGN(X + 4, 4), (5) can be converted to:
(void *)rec + ALIGN(be16_to_cpu(rec->len) + 6, 4) (6)
5. Subsituting 6 in (6) to sizeof(*rec) we get:
(void *)rec + ALIGN(be16_to_cpu(rec->len) + sizeof(*rec), 4) (7)
Using expression (7) should make it more clear that next record is
located by adding full size of the current record (payload + auxiliary
data) aligned to 4 bytes, to the location of the current one. No
functional change intended.
Cc: Chris Healy <cphe...@gmail.com>
Cc: Kyle McMartin <k...@kernel.org>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Masahiro Yamada <yamada.masah...@socionext.com>
Cc: David Woodhouse <dw...@infradead.org>
Cc: Greg Kroah-Hartman <gre...@linuxfoundation.org>
Cc: linux-kernel <linux-kernel@vger.kernel.org>
Signed-off-by: Andrey Smirnov <andrew.smir...@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
include/linux/ihex.h | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/include/linux/ihex.h b/include/linux/ihex.h
index 9130f307a420..98cb5ce0b0a0 100644
--- a/include/linux/ihex.h
+++ b/include/linux/ihex.h
@@ -21,14 +21,18 @@ struct ihex_binrec {
uint8_t data[0];
} __attribute__((packed));
+static inline uint16_t ihex_binrec_size(const struct ihex_binrec *p)
+{
+ return be16_to_cpu(p->len) + sizeof(*p);
+}
+
/* Find the next record, taking into account the 4-byte alignment */
static inline const struct ihex_binrec *
__ihex_next_binrec(const struct ihex_binrec *rec)
{
- int next = ((be16_to_cpu(rec->len) + 5) & ~3) - 2;
- rec = (void *)&rec->data[next];
+ const void *p = rec;
- return rec;
+ return p + ALIGN(ihex_binrec_size(rec), 4);
}
static inline const struct ihex_binrec *
--
2.20.1
