linux-kernel - Re: [PATCH v14 mfd 9/9] mfd: ocelot: add support for the vsc7512 chip via spi

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Message-ID: <YuiJLK8ncbHH3OhE@euler>
Date:   Mon, 1 Aug 2022 19:17:16 -0700
From:   Colin Foster <colin.foster@...advantage.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Terry Bowman <terry.bowman@....com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Wolfram Sang <wsa@...nel.org>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Steen Hegelund <Steen.Hegelund@...rochip.com>,
        Lars Povlsen <lars.povlsen@...rochip.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Russell King <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>, katie.morris@...advantage.com
Subject: Re: [PATCH v14 mfd 9/9] mfd: ocelot: add support for the vsc7512
 chip via spi

Hi Andy,

Apologies for the late response. Everything seemed straightforward, but
as I was implementing your suggestions one thing came out.

I just want to make sure my implementation isn't horribly off before the
next patch set.

Specifically this question (copied from below):
> I'm wondering if you can use in both cases
> spi_message_init_with_transfers().

> > +static int ocelot_spi_regmap_bus_read(void *context, const void *reg, size_t reg_size,
> > +                                     void *val, size_t val_size)
> > +{
> > +       struct spi_transfer tx, padding, rx;

struct spi_transfer xfers[3] = {0};
struct spi_transfer *xfer_tok = xfers;

> > +       struct device *dev = context;
> > +       struct ocelot_ddata *ddata;
> > +       struct spi_device *spi;
> > +       struct spi_message msg;
> > +
> > +       ddata = dev_get_drvdata(dev);
> > +       spi = to_spi_device(dev);
> > +
> > +       spi_message_init(&msg);
> > +
> > +       memset(&tx, 0, sizeof(tx));
> > +
> > +       tx.tx_buf = reg;
> > +       tx.len = reg_size;

xfer_tok->tx_buf = reg;
xfer_tok->len = reg_size;
xfer_tok++;

> > +
> > +       spi_message_add_tail(&tx, &msg);
> > +
> > +       if (ddata->spi_padding_bytes) {
> > +               memset(&padding, 0, sizeof(padding));
> > +
> > +               padding.len = ddata->spi_padding_bytes;
> > +               padding.tx_buf = ddata->dummy_buf;
> > +               padding.dummy_data = 1;

xfer_tok->len
xfer_tok->tx_buf
xfer_tok->dummy_data
xfer_tok++;

> > +
> > +               spi_message_add_tail(&padding, &msg);
> > +       }
> > +
> > +       memset(&rx, 0, sizeof(rx));
> > +       rx.rx_buf = val;
> > +       rx.len = val_size;

xfer_tok->rx_buf
xfer_tok->len
xfer_tok++;

> > +
> > +       spi_message_add_tail(&rx, &msg);

spi_message_init_with_transfers(&msg, xfers, xfer_tok - xfers);

> 
> I'm wondering if you can use in both cases
> spi_message_init_with_transfers().

I could see that implementation getting the response of "what the heck
were you thinking" or "that looks alright" and I honestly have no idea
which pool it will fall into.

> 
> > +       return spi_sync(spi, &msg);
> > +}
>