linux-kernel - Re: [PATCH 2/2] drivers: ipmi: Modify max length of IPMB packet

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Message-ID: <7BC487D6-6ACA-46CE-A751-8367FEDEE647@fb.com>
Date:   Tue, 12 Nov 2019 19:56:34 +0000
From:   Vijay Khemka <vijaykhemka@...com>
To:     "minyard@....org" <minyard@....org>
CC:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "openipmi-developer@...ts.sourceforge.net" 
        <openipmi-developer@...ts.sourceforge.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "cminyard@...sta.com" <cminyard@...sta.com>,
        "asmaa@...lanox.com" <asmaa@...lanox.com>,
        "joel@....id.au" <joel@....id.au>,
        "linux-aspeed@...ts.ozlabs.org" <linux-aspeed@...ts.ozlabs.org>,
        Sai Dasari <sdasari@...com>
Subject: Re: [PATCH 2/2] drivers: ipmi: Modify max length of IPMB packet



On 11/12/19, 4:48 AM, "Corey Minyard" <tcminyard@...il.com on behalf of minyard@....org> wrote:

    On Mon, Nov 11, 2019 at 06:36:10PM -0800, Vijay Khemka wrote:
    > As per IPMB specification, maximum packet size supported is 255,
    > modified Max length to 240 from 128 to accommodate more data.
    
    I couldn't find this in the IPMB specification.
    
    IIRC, the maximum on I2C is 32 byts, and table 6-9 in the IPMI spec,
    under "IPMB Output" states: The IPMB standard message length is
    specified as 32 bytes, maximum, including slave address.

We are using IPMI OEM messages and our response size is around 150 bytes
For some of responses. That's why I had set it to 240 bytes.
    
    I'm not sure where 128 came from, but maybe it should be reduced to 31.
    
    -corey
    
    > 
    > Signed-off-by: Vijay Khemka <vijaykhemka@...com>
    > ---
    >  drivers/char/ipmi/ipmb_dev_int.c | 2 +-
    >  1 file changed, 1 insertion(+), 1 deletion(-)
    > 
    > diff --git a/drivers/char/ipmi/ipmb_dev_int.c b/drivers/char/ipmi/ipmb_dev_int.c
    > index 2419b9a928b2..7f9198bbce96 100644
    > --- a/drivers/char/ipmi/ipmb_dev_int.c
    > +++ b/drivers/char/ipmi/ipmb_dev_int.c
    > @@ -19,7 +19,7 @@
    >  #include <linux/spinlock.h>
    >  #include <linux/wait.h>
    >  
    > -#define MAX_MSG_LEN		128
    > +#define MAX_MSG_LEN		240
    >  #define IPMB_REQUEST_LEN_MIN	7
    >  #define NETFN_RSP_BIT_MASK	0x4
    >  #define REQUEST_QUEUE_MAX_LEN	256
    > -- 
    > 2.17.1
    >