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Message-ID: <20190123213229.GA17772@lunn.ch> Date: Wed, 23 Jan 2019 22:32:29 +0100 From: Andrew Lunn <andrew@...n.ch> To: René van Dorst <opensource@...rst.com> Cc: Florian Fainelli <f.fainelli@...il.com>, Heiner Kallweit <hkallweit1@...il.com>, "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org Subject: Re: [PATCH] sfp: sfp_read: split-up request when hw rx buffer is too small. On Wed, Jan 23, 2019 at 10:20:46PM +0100, René van Dorst wrote: > Without this patch sfp code retries to read the full struct sfp_eeprom_id > id out of the SFP eeprom. Sizeof(id) is 96 bytes. > My i2c hardware, Mediatek mt7621, has a rx buffer of 64 bytes. > So sfp_read gets -NOSUPPORTED back on his turn return -EAGAIN. > Same issue is with the SFP_EXT_STATUS data which is 92 bytes. > > By split-up the request in multiple smaller requests with a max size of i2c > max_read_len, we can readout the SFP module successfully. > > Tested with MT7621 and two Fiberstore modules SFP-GB-GE-T and SFP-GE-BX. > > Signed-off-by: René van Dorst <opensource@...rst.com> > --- > drivers/net/phy/sfp.c | 23 ++++++++++++++++++++++- > 1 file changed, 22 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c > index fd8bb998ae52..1352a19571cd 100644 > --- a/drivers/net/phy/sfp.c > +++ b/drivers/net/phy/sfp.c > @@ -367,7 +367,28 @@ static void sfp_set_state(struct sfp *sfp, unsigned int state) > > static int sfp_read(struct sfp *sfp, bool a2, u8 addr, void *buf, size_t len) > { > - return sfp->read(sfp, a2, addr, buf, len); > + const struct i2c_adapter_quirks *q = sfp->i2c->quirks; > + int ret; > + size_t rx_bytes = 0; > + > + /* Many i2c hw have limited rx buffers, split-up request when needed. */ > + while ((q->max_read_len) && (len > q->max_read_len)) { > + ret = sfp->read(sfp, a2, addr, buf, q->max_read_len); Hi René I think you want to pass MIN(len, q->max_read_len) to read(). > + if (ret < 0) > + return ret; > + rx_bytes += ret; > + addr += q->max_read_len; > + buf += q->max_read_len; > + len -= q->max_read_len; I would prefer you add ret, not q->max_read_len. There is a danger it returned less bytes than you asked for. > + } > + > + ret = sfp->read(sfp, a2, addr, buf, len); > + if (ret < 0) > + return ret; > + > + rx_bytes += ret; > + > + return rx_bytes; > } > > static int sfp_write(struct sfp *sfp, bool a2, u8 addr, void *buf, size_t len) Doesn't write need the same handling? Thanks Andrew
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