From c956d6d820f5196fecde268a9334df557ad3c3b6 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Thu, 13 Nov 2014 09:04:42 -0600
Subject: [PATCH 1/2] =?UTF-8?q?Add=20support=20for=20seeking=20in=20BCH.?=
 =?UTF-8?q?=20=20From=20S=C3=A9bastien=20Lorquet.?=
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit

---
 drivers/bch/bchdev_driver.c | 71 +++++++++++++++++++++++++++++++++++--
 1 file changed, 69 insertions(+), 2 deletions(-)

diff --git a/drivers/bch/bchdev_driver.c b/drivers/bch/bchdev_driver.c
index b4517065237..7e3d2abcb37 100644
--- a/drivers/bch/bchdev_driver.c
+++ b/drivers/bch/bchdev_driver.c
@@ -70,6 +70,7 @@
 
 static int     bch_open(FAR struct file *filep);
 static int     bch_close(FAR struct file *filep);
+static off_t   bch_seek(FAR struct file *filep, off_t offset, int whence);
 static ssize_t bch_read(FAR struct file *filep, FAR char *buffer,
                  size_t buflen);
 static ssize_t bch_write(FAR struct file *filep, FAR const char *buffer,
@@ -87,7 +88,7 @@ const struct file_operations bch_fops =
   bch_close, /* close */
   bch_read,  /* read */
   bch_write, /* write */
-  0,         /* seek */
+  bch_seek,  /* seek */
   bch_ioctl  /* ioctl */
 #ifndef CONFIG_DISABLE_POLL
   , 0        /* poll */
@@ -168,7 +169,73 @@ static int bch_close(FAR struct file *filep)
 }
 
 /****************************************************************************
- * Name:bch_read
+ * Name: bch_seek
+ ****************************************************************************/
+
+static off_t bch_seek(FAR struct file *filep, off_t offset, int whence)
+{
+  FAR struct inode *inode = filep->f_inode;
+  FAR struct bchlib_s *bch;
+  off_t newpos;
+  int ret;
+
+  DEBUGASSERT(inode && inode->i_private);
+
+  bch = (FAR struct bchlib_s *)inode->i_private;
+  bchlib_semtake(bch);
+
+  /* Determine the new, requested file position */
+
+  switch (whence)
+    {
+    case SEEK_CUR:
+      newpos = filep->f_pos + offset;
+      break;
+
+    case SEEK_SET:
+      newpos = offset;
+      break;
+
+    case SEEK_END:
+      newpos = bch->sectsize * bch->nsectors + offset;
+      break;
+
+    default:
+      /* Return EINVAL if the whence argument is invalid */
+
+      bchlib_semgive(bch);
+      return -EINVAL;
+    }
+
+  /* Opengroup.org:
+   *
+   *  "The lseek() function shall allow the file offset to be set beyond the end
+   *   of the existing data in the file. If data is later written at this point,
+   *   subsequent reads of data in the gap shall return bytes with the value 0
+   *   until data is actually written into the gap."
+   *
+   * We can conform to the first part, but not the second.  But return EINVAL if
+   *
+   *  "...the resulting file offset would be negative for a regular file, block
+   *   special file, or directory."
+   */
+
+  if (newpos >= 0)
+    {
+      filep->f_pos = newpos;
+      ret = newpos;
+    }
+  else
+    {
+      ret = -EINVAL;
+    }
+
+  bchlib_semgive(bch);
+  return ret;
+}
+
+/****************************************************************************
+ * Name: bch_read
  ****************************************************************************/
 
 static ssize_t bch_read(FAR struct file *filep, FAR char *buffer, size_t len)

From e0270c568b3f8605555f0efb115fe8da56fa8895 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Thu, 13 Nov 2014 09:07:27 -0600
Subject: [PATCH 2/2] Update ChangeLog

---
 ChangeLog | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 546d4cd8221..45534fa9804 100755
--- a/ChangeLog
+++ b/ChangeLog
@@ -8954,3 +8954,5 @@
 	* arch/arm/src/efm32/efm32_clockconfig.c, configs/efm32gg-stk3700/README.txt
 	  and include/board.h:  Fixes to get the EFM32GG-STK3700 basic NSH
 	  configuration running.  It works! (2014-11-12).
+	* drivers/bch/bchdev_driver.c: Add support for seeking in BCH.  From
+	  Sébastien Lorquet. (2014-11-13).