From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wi0-x235.google.com ([2a00:1450:400c:c05::235]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1Zoas7-0005el-5C for linux-mtd@lists.infradead.org; Tue, 20 Oct 2015 17:38:51 +0000 Received: by wicfx6 with SMTP id fx6so56754756wic.1 for ; Tue, 20 Oct 2015 10:38:29 -0700 (PDT) Subject: Re: [PATCH] mtd: spi-nor: handle controller driver limitations in spi_nor_read To: Brian Norris References: <5614182B.7060304@gmail.com> Cc: linux-mtd@lists.infradead.org From: Heiner Kallweit Message-ID: <56267C0D.1020906@gmail.com> Date: Tue, 20 Oct 2015 19:38:21 +0200 MIME-Version: 1.0 In-Reply-To: <5614182B.7060304@gmail.com> 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: , Any feedback on this patch and the two others I sent on Oct 6th/7th? Thanks Am 06.10.2015 um 20:51 schrieb Heiner Kallweit: > 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; > } > >