linux-kernel - [PATCH] char: xillybus: Fix internal data structure initialization

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Date:	Wed, 24 Feb 2016 10:40:51 +0200
From:	Eli Billauer <eli.billauer@...il.com>
To:	arnd@...db.de, gregkh@...uxfoundation.org
Cc:	linux-kernel@...r.kernel.org, Eli Billauer <eli.billauer@...il.com>
Subject: [PATCH] char: xillybus: Fix internal data structure initialization

A couple of fields in a data structure, which is used by the driver only,
were not initialized properly during the driver's setup.

The primary issue with this bug was that channel->wr_buf_size remained zero,
so calls to dma_sync_single_for_cpu() took place with zero size, and
consequently did nothing.

This had a rather minimal practical impact, because

(a) these calls are NOPs on Intel/AMD platforms, as well as other platforms
    with coherent cache, and
(b) it's extremely rare that any cache line would survive between two reads
    from a given DMA buffer

Hence no significant practical difference is expected with this patch.

Signed-off-by: Eli Billauer <eli.billauer@...il.com>
---
 drivers/char/xillybus/xillybus_core.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/drivers/char/xillybus/xillybus_core.c b/drivers/char/xillybus/xillybus_core.c
index 77d6c12..dcd19f3 100644
--- a/drivers/char/xillybus/xillybus_core.c
+++ b/drivers/char/xillybus/xillybus_core.c
@@ -509,7 +509,7 @@ static int xilly_setupchannels(struct xilly_endpoint *ep,
 			channel->log2_element_size = ((format > 2) ?
 						      2 : format);
 
-			bytebufsize = channel->rd_buf_size = bufsize *
+			bytebufsize = bufsize *
 				(1 << channel->log2_element_size);
 
 			buffers = devm_kcalloc(dev, bufnum,
@@ -523,6 +523,7 @@ static int xilly_setupchannels(struct xilly_endpoint *ep,
 
 		if (!is_writebuf) {
 			channel->num_rd_buffers = bufnum;
+			channel->rd_buf_size = bytebufsize;
 			channel->rd_allow_partial = allowpartial;
 			channel->rd_synchronous = synchronous;
 			channel->rd_exclusive_open = exclusive_open;
@@ -533,6 +534,7 @@ static int xilly_setupchannels(struct xilly_endpoint *ep,
 						   bufnum, bytebufsize);
 		} else if (channelnum > 0) {
 			channel->num_wr_buffers = bufnum;
+			channel->wr_buf_size = bytebufsize;
 
 			channel->seekable = seekable;
 			channel->wr_supports_nonempty = supports_nonempty;
-- 
1.7.2.3