From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wi0-x233.google.com ([2a00:1450:400c:c05::233]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZjXT6-00022p-SV for linux-mtd@lists.infradead.org; Tue, 06 Oct 2015 19:00:10 +0000 Received: by wicfx3 with SMTP id fx3so180666994wic.1 for ; Tue, 06 Oct 2015 11:59:47 -0700 (PDT) From: Heiner Kallweit Subject: [PATCH] mtd: spi-nor: handle controller driver limitations in spi_nor_read To: Brian Norris Cc: linux-mtd@lists.infradead.org Message-ID: <5614182B.7060304@gmail.com> Date: Tue, 6 Oct 2015 20:51:23 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Back in May there was a discussion on how to handle controller driver limitations like max message size (e.g. spi-fsl-espi supports message sizes up to 64Kb only). According to Brian extending the API might not be needed and a better handling of the returned actual_length of the message should be sufficient. Following the suggestion this patch supports reading chunks. As long as something was read also errors (like -EMSGSIZE) are ignored. Afterwards related hacks can be removed from affected controller drivers, making them work with any protocol driver. Currently e.g. spi-fsl-espi implicitely assumes that longer reads come from m25p80 protocol driver (if second transfer in message is a read and first transfer is a send then bytes 2-4 of the send are assumed to be a 3 byte address of a flash read). Signed-off-by: Heiner Kallweit --- drivers/mtd/spi-nor/spi-nor.c | 15 ++++++++++++++- 1 file changed, 14 insertions(+), 1 deletion(-) diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c index 4be41fb..17b5239 100644 --- a/drivers/mtd/spi-nor/spi-nor.c +++ b/drivers/mtd/spi-nor/spi-nor.c @@ -761,6 +761,7 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen, u_char *buf) { struct spi_nor *nor = mtd_to_spi_nor(mtd); + size_t bytes_read, pos = 0; int ret; dev_dbg(nor->dev, "from 0x%08x, len %zd\n", (u32)from, len); @@ -769,9 +770,21 @@ static int spi_nor_read(struct mtd_info *mtd, loff_t from, size_t len, if (ret) return ret; - ret = nor->read(nor, from, len, retlen, buf); + /* Consider the case that a controller driver is not able + * to read all requested bytes at once. It might return + * an error and the number of bytes read. + * Therefore ignore errors as long as something was read. + */ + do { + bytes_read = 0; + ret = nor->read(nor, from + pos, len - pos, + &bytes_read, buf + pos); + pos += bytes_read; + } while (pos < len && bytes_read); spi_nor_unlock_and_unprep(nor, SPI_NOR_OPS_READ); + + *retlen = pos; return ret; } -- 2.6.0