netdev - Re: [PATCH net-next 3/3] Add capability to retrieve plug-in module EEPROM

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Date:	Tue, 24 Apr 2012 18:43:12 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Stuart Hodgson <smhodgson@...arflare.com>
CC:	<netdev@...r.kernel.org>, <bruce.w.allan@...el.com>,
	<decot@...gle.com>, <alexander.h.duyck@...el.com>,
	<davem@...emloft.net>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 3/3] Add capability to retrieve plug-in module
 EEPROM

On Thu, 2012-04-19 at 16:39 +0100, Stuart Hodgson wrote:
> Currently allows for SFP+ eeprom to be returned using the ethtool API.
> This can be extended in future to handle different eeprom formats
> and sizes
[...]
> --- a/drivers/net/ethernet/sfc/mcdi_phy.c
> +++ b/drivers/net/ethernet/sfc/mcdi_phy.c
> @@ -304,6 +304,26 @@ static u32 mcdi_to_ethtool_media(u32 media)
>  	}
>  }
> 
> +static u32 mcdi_to_module_eeprom_len(u32 media)
> +{
> +	switch (media) {
> +	case MC_CMD_MEDIA_SFP_PLUS:
> +		return ETH_MODULE_SFF_8079_LEN;
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static u32 mcdi_to_module_eeprom_type(u32 media)
> +{
> +	switch (media) {
> +	case MC_CMD_MEDIA_SFP_PLUS:
> +		return ETH_MODULE_SFF_8079;
> +	default:
> +		return 0;
> +	}
> +}

These functions ended up unused, so don't add them.  You should have got
a compiler warning about this...

>  static int efx_mcdi_phy_probe(struct efx_nic *efx)
>  {
>  	struct efx_mcdi_phy_data *phy_data;
> @@ -739,6 +759,95 @@ static const char *efx_mcdi_phy_test_name(struct efx_nic *efx,
>  	return NULL;
>  }
> 
> +#define SFP_PAGE_SIZE	128
> +#define SFP_NUM_PAGES	2
> +static int efx_mcdi_phy_get_module_eeprom(struct efx_nic *efx,
> +					  struct ethtool_eeprom *ee, u8 *data)
> +{
> +	u8 outbuf[MC_CMD_GET_PHY_MEDIA_INFO_OUT_LENMAX];
> +	u8 inbuf[MC_CMD_GET_PHY_MEDIA_INFO_IN_LEN];
> +	size_t outlen;
> +	int rc;
> +	unsigned int payload_len;
> +	unsigned int copied = 0;
> +	unsigned int space_remaining = ee->len;
> +	unsigned int page;
> +	unsigned int page_off;
> +	unsigned int to_copy;
> +	u8 *user_data = data;
> +
> +	if (ee->offset > (SFP_PAGE_SIZE * SFP_NUM_PAGES))
> +		return -EINVAL;

Please also add this sanity-check:

	BUILD_BUG_ON(SFP_PAGE_SIZE * SFP_NUM_PAGES != ETH_MODULE_SFF_8079_LEN);

> +	page_off = (ee->offset % SFP_PAGE_SIZE);
> +	page = (ee->offset > SFP_PAGE_SIZE) ? 1 : 0;

Off-by-one error; the comparison should be >=.  Why not use the
straightforward calculation:

	page = ee->offset / SFP_PAGE_SIZE;

[...]
> +static int efx_mcdi_phy_get_module_info(struct efx_nic *efx,
> +					struct ethtool_modinfo *modinfo)
> +{
> +	/* This will return a length of the eeprom
> +	 * type of the module that was detected during the probe,
> +	 * if not modules inserted then phy_data will be NULL */
> +	struct efx_mcdi_phy_data *phy_cfg;
> +
> +	phy_cfg = efx->phy_data;
> +	modinfo->eeprom_len = 0;
> +	modinfo->type = 0;
> +
> +	switch (phy_cfg->media) {
> +	case MC_CMD_MEDIA_SFP_PLUS:
> +		modinfo->type = ETH_MODULE_SFF_8079;
> +		modinfo->eeprom_len = ETH_MODULE_SFF_8079_LEN;
> +		break;
> +	default:

The default case should return -EOPNOTSUPP, just as if we didn't
implement this operation at all.  And there's no need to set
modinfo->{type,eeprom_len} to 0 in that case.

Ben.

> +		break;
> +	}
> +
> +	return 0;
> +}
[...]

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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