linux-kernel - Re: [RESEND v12] can: usb: etas_es58X: add support for ETAS ES58X CAN USB interfaces

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Message-ID: <CAMZ6RqJ8j0yqw1Sa1dbLpakBSuKie5xpYMpg6oQFG_MuE3sWkw@mail.gmail.com>
Date:   Wed, 10 Mar 2021 03:11:28 +0900
From:   Vincent MAILHOL <mailhol.vincent@...adoo.fr>
To:     Jimmy Assarsson <jimmyassarsson@...il.com>
Cc:     Arunachalam Santhanam <arunachalam.santhanam@...bosch.com>,
        open list <linux-kernel@...r.kernel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        linux-can <linux-can@...r.kernel.org>
Subject: Re: [RESEND v12] can: usb: etas_es58X: add support for ETAS ES58X CAN
 USB interfaces

On Wed. 10 Mar 2021 at 02:27, Jimmy Assarsson <jimmyassarsson@...il.com> wrote:
>
> Hi Vincent,
>
> On 2021-03-09 13:09, Vincent Mailhol wrote:
> > This driver supports the ES581.4, ES582.1 and ES584.1 interfaces from
> > ETAS GmbH (https://www.etas.com/en/products/es58x.php).
> ...
> > diff --git a/drivers/net/can/usb/etas_es58x/es58x_core.c b/drivers/net/can/usb/etas_es58x/es58x_core.c
> > new file mode 100644
> > index 000000000000..31f907a7b75f
> > --- /dev/null
> > +++ b/drivers/net/can/usb/etas_es58x/es58x_core.c
> ...
> > +/**
> > + * es58x_add_skb_idx() - Increment an index of the loopback FIFO.
> > + * @priv: ES58X private parameters related to the network device.
> > + * @idx: address of the index to be incremented.
> > + * @a: the increment. Must be positive and less or equal to
> > + *   @priv->can.echo_skb_max.
> > + *
> > + * Do a modulus addition: set *@idx to (*@idx + @a) %
> > + * @priv->can.echo_skb_max.
> > + *
> > + * Rationale: the modulus operator % takes a decent amount of CPU
> > + * cycles (c.f. other division functions such as
> > + * include/linux/math64.h:iter_div_u64_rem()).
> > + */
> > +static __always_inline void es58x_add_skb_idx(struct es58x_priv *priv,
> > +                                           u16 *idx, u16 a)
>
> Never used?

Indeed, this is a leftover. Should have been removed in v11 when I
made the device FIFO size a power of two.
I was not warned by the compiler, probably because this is an inline function.

> ...
> > +/**
> > + * es58x_get_product_info() - Get the product information and print them.
> > + * @es58x_dev: ES58X device.
> > + *
> > + * Do a synchronous call to get the product information.
> > + *
> > + * Return: zero on success, errno when any error occurs.
> > + */
> > +static int es58x_get_product_info(struct es58x_device *es58x_dev)
> > +{
> > +     struct usb_device *udev = es58x_dev->udev;
> > +     const int es58x_prod_info_idx = 6;
> > +     /* Empirical tests show a prod_info length of maximum 83,
> > +      * below should be more than enough.
> > +      */
> > +     const size_t prod_info_len = 127;
> > +     char *prod_info;
> > +     int ret;
> > +
> > +     prod_info = kmalloc(prod_info_len, GFP_KERNEL);
> > +     if (!prod_info)
> > +             return -ENOMEM;
> > +
> > +     ret = usb_string(udev, es58x_prod_info_idx, prod_info, prod_info_len);
> > +     if (ret < 0) {
> > +             dev_err(es58x_dev->dev,
> > +                     "%s: Could not read the product info: %pe\n",
> > +                     __func__, ERR_PTR(ret));
>
> Missing free

Absolutely!

> > +             return ret;
> > +     } else if (ret >= prod_info_len - 1) {
> > +             dev_warn(es58x_dev->dev,
> > +                      "%s: Buffer is too small, result might be truncated\n",
> > +                      __func__);
> > +     }
> > +     dev_info(es58x_dev->dev, "Product info: %s\n", prod_info);
> > +     kfree(prod_info);
> > +
> > +     return 0;
> > +}

Thanks for the two findings, both will be fixed in v13.


Yours sincerely,
Vincent