netdev - RE: [PATCH] net-bnx2x: Fix byte order problem on NVRAM writes

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Message-ID: <979A8436335E3744ADCD3A9F2A2B68A52AEABE99@SJEXCHMB10.corp.ad.broadcom.com>
Date:	Tue, 22 Oct 2013 13:30:41 +0000
From:	"Yuval Mintz" <yuvalmin@...adcom.com>
To:	"Nate Klein" <nxk@...gle.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
cc:	"Eilon Greenstein" <eilong@...adcom.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] net-bnx2x: Fix byte order problem on NVRAM writes

> Tested:
>     ethtool -e eth0 raw on >first.nvram
>     ethtool -E eth0 <first.nvram
>     ethtool -e eth0 raw on >second.nvram
>     cmp first.nvram second.nvram || ethtool -E eth0 <second.nvram
>     (No output means pass.)

Hi Nate,

We're aware of this `bug' for some time - we've encountered it when
trying to fix the endian sparse warnings in the driver.

Sadly, there are already existing user applications that assume that this is 
the driver's behaviour - i.e., those applications prepare their buffers in a 
manner which assumes the endian of the writes; changing this write will 
cause those tools to break.
That's why we haven't fixed the issue before, and cannot support such a
fix. We're more than willing to document it somewhere, if that seems 
useful to anyone.

Thanks,
Yuval

> ---
>  drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c
> b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c
> index 8213cc8..35671fb 100644
> --- a/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c
> +++ b/drivers/net/ethernet/broadcom/bnx2x/bnx2x_ethtool.c
> @@ -1549,7 +1549,7 @@ static int bnx2x_nvram_write_dword(struct bnx2x
> *bp, u32 offset, u32 val,
>  	REG_WR(bp, MCP_REG_MCPR_NVM_COMMAND,
> MCPR_NVM_COMMAND_DONE);
> 
>  	/* write the data */
> -	REG_WR(bp, MCP_REG_MCPR_NVM_WRITE, val);
> +	REG_WR(bp, MCP_REG_MCPR_NVM_WRITE, cpu_to_be32(val));
> 
>  	/* address of the NVRAM to write to */
>  	REG_WR(bp, MCP_REG_MCPR_NVM_ADDR,
> --


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