From d0c3c16e995308838d724775cd8624a69907046e Mon Sep 17 00:00:00 2001
From: Vladimir Serbinenko <phcoder@gmail.com>
Date: Wed, 29 Jan 2014 23:49:51 +0100
Subject: [PATCH 054/198] * grub-core/disk/ahci.c: Properly handle transactions
 with no transferred data.

---
 ChangeLog             | 5 +++++
 grub-core/disk/ahci.c | 7 +++++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 15300b0..bc1ab23 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2014-01-29  Vladimir Serbinenko  <phcoder@gmail.com>
 
+	* grub-core/disk/ahci.c: Properly handle transactions with no
+	transferred data.
+
+2014-01-29  Vladimir Serbinenko  <phcoder@gmail.com>
+
 	* grub-core/disk/ahci.c: Add safety cleanups.
 
 2014-01-29  Vladimir Serbinenko  <phcoder@gmail.com>
diff --git a/grub-core/disk/ahci.c b/grub-core/disk/ahci.c
index 643e691..fdd40c6 100644
--- a/grub-core/disk/ahci.c
+++ b/grub-core/disk/ahci.c
@@ -932,7 +932,10 @@ grub_ahci_readwrite_real (struct grub_ahci_device *dev,
   if (parms->size > GRUB_AHCI_PRDT_MAX_CHUNK_LENGTH)
     return grub_error (GRUB_ERR_BUG, "too big data buffer");
 
-  bufc = grub_memalign_dma32 (1024, parms->size + (parms->size & 1));
+  if (parms->size)
+    bufc = grub_memalign_dma32 (1024, parms->size + (parms->size & 1));
+  else
+    bufc = grub_memalign_dma32 (1024, 512);
 
   grub_dprintf ("ahci", "AHCI tfd = %x, CL=%p\n",
 		dev->hba->ports[dev->port].task_file_data,
@@ -942,7 +945,7 @@ grub_ahci_readwrite_real (struct grub_ahci_device *dev,
     = (5 << GRUB_AHCI_CONFIG_CFIS_LENGTH_SHIFT)
     //    | GRUB_AHCI_CONFIG_CLEAR_R_OK
     | (0 << GRUB_AHCI_CONFIG_PMP_SHIFT)
-    | (1 << GRUB_AHCI_CONFIG_PRDT_LENGTH_SHIFT)
+    | ((parms->size ? 1 : 0) << GRUB_AHCI_CONFIG_PRDT_LENGTH_SHIFT)
     | (parms->cmdsize ? GRUB_AHCI_CONFIG_ATAPI : 0)
     | (parms->write ? GRUB_AHCI_CONFIG_WRITE : GRUB_AHCI_CONFIG_READ)
     | (parms->taskfile.cmd == 8 ? (1 << 8) : 0);
-- 
2.7.4