linux-kernel - Re: [PATCH v13] platform/mellanox: Add TmFifo driver for Mellanox BlueField Soc

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Message-ID: <CAHp75Vfqi4Z3OrMsgeTJamJ61b7urAGkU2CKng8+Y-HvOGTvBQ@mail.gmail.com>
Date:   Thu, 11 Apr 2019 17:13:27 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Liming Sun <lsun@...lanox.com>
Cc:     David Woods <dwoods@...lanox.com>,
        Andy Shevchenko <andy@...radead.org>,
        Darren Hart <dvhart@...radead.org>,
        Vadim Pasternak <vadimp@...lanox.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v13] platform/mellanox: Add TmFifo driver for Mellanox
 BlueField Soc

On Sun, Apr 7, 2019 at 5:05 AM Liming Sun <lsun@...lanox.com> wrote:

> > > + * mlxbf_tmfifo_msg_hdr - Structure of the TmFifo message header
> > > + * @type: message type
> > > + * @len: payload length
> > > + * @u: 64-bit union data
> > > + */
> > > +union mlxbf_tmfifo_msg_hdr {
> > > +       struct {
> > > +               u8 type;
> > > +               __be16 len;
> > > +               u8 unused[5];
> > > +       } __packed;
> > > +       u64 data;
> >
> > I'm not sure I understand how you can distinguish which field of union to use?
> > Isn't here some type missed?
>
> Updated the comment in v14.
>
> This message header is a union of struct and u64 data.
> The 'struct' has
> type and length field which are used to encode & decode the message.
> The 'data' field is used to read/write the message header from/to the FIFO.

Something fishy here.

You are using a structure of data which you would like to write with
one call? Perhaps you need to construct this on-the-fly.
Moreover, the __be memeber is used in a data which is written as LE.
This needs more explanation.

-- 
With Best Regards,
Andy Shevchenko