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From:   Alan Mikhak <alan.mikhak@sifive.com>
To:     linux-kernel@vger.kernel.org, martin.petersen@oracle.com,
        alexios.zavras@intel.com, ming.lei@redhat.com,
        gregkh@linuxfoundation.org, tglx@linutronix.de, jgg@ziepe.ca,
        christophe.leroy@c-s.fr, thellstrom@vmware.com,
        galpress@amazon.com, palmer@sifive.com, paul.walmsley@sifive.com
Cc:     Alan Mikhak <alan.mikhak@sifive.com>
Subject: [PATCH] scatterlist: Comment on pages for sg_set_page()
Date:   Tue,  1 Oct 2019 11:32:50 -0700
Message-Id: <1569954770-11477-1-git-send-email-alan.mikhak@sifive.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

From: Alan Mikhak <alan.mikhak@sifive.com>

Update the description of sg_set_page() to communicate current
requirements for the page pointer parameter.

Signed-off-by: Alan Mikhak <alan.mikhak@sifive.com>
---
 include/linux/scatterlist.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h
index 6eec50fb36c8..6dda865893aa 100644
--- a/include/linux/scatterlist.h
+++ b/include/linux/scatterlist.h
@@ -112,6 +112,12 @@ static inline void sg_assign_page(struct scatterlist *sg, struct page *page)
  *   of the page pointer. See sg_page() for looking up the page belonging
  *   to an sg entry.
  *
+ *   Scatterlist currently expects the page parameter to be a pointer to
+ *   a page that is backed by a page struct.
+ *
+ *   Page pointers derived from addresses obtained from ioremap() are
+ *   currently not supported since they require use of iomem safe memcpy.
+ *
  **/
 static inline void sg_set_page(struct scatterlist *sg, struct page *page,
 			       unsigned int len, unsigned int offset)
-- 
2.7.4