linux-kernel - [PATCH 1/1] memstick: fix the bit shift problem for JMicron 38x controllers in ARM platform

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Message-Id: <201105160518.p4G5IqrK014870@jmr105.jmicron.com>
Date:	Mon, 16 May 2011 13:18:52 +0800
From:	"Aries Lee" <arieslee@...cron.com>
To:	<linux-kernel@...r.kernel.org>
Cc:	<devinchiu@...cron.com>, "'Aries Lee'" <arieslee@...cron.com>,
	<oakad@...oo.com>
Subject: [PATCH 1/1] memstick: fix the bit shift problem for JMicron 38x controllers in ARM platform

If x86 architecture, an unsigned variable shift more than 31 times means a
rotation.
But in some architecture, shift 32 bit or more will give a zero value.
For example, 
An unsigned int variable of 0x11223344 runs the operation "<< 32",
In x86 architecture, its value is still 0x11223344
But its value will change as 0x00000000 in ARM.

This patch try to fix those architecture-specific code, and made it both
work in x86 and the other architecture.

Signed-off-by: Aries Lee <arieslee@...cron.com>
---
diff --git a/drivers/memstick/host/jmb38x_ms.c
b/drivers/memstick/host/jmb38x_ms.c
index d89d925..272e89c 100644
--- a/drivers/memstick/host/jmb38x_ms.c
+++ b/drivers/memstick/host/jmb38x_ms.c
@@ -287,8 +287,8 @@ static unsigned int jmb38x_ms_write_reg_data(struct
jmb38x_ms_host *host,
 		return off;
 
 	while (host->io_pos < 8 && length) {
-		host->io_word[1] &= ~(0xff << (host->io_pos * 8));
-		host->io_word[1] |=  buf[off++] << (host->io_pos * 8);
+		host->io_word[1] &= ~(0xff << ((host->io_pos-4) * 8));
+		host->io_word[1] |=  buf[off++] << ((host->io_pos-4) * 8);
 		host->io_pos++;
 		length--;
 	}


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