[PATCH v5 8/8] virtio: rng: Add a random number generator(rng) driver

[Sughosh Ganu]

On Fri, 27 Dec 2019 at 12:42, Heinrich Schuchardt <xypron.glpk at gmx.de>
wrote:

> On 12/26/19 6:25 PM, Sughosh Ganu wrote:
> > Add a driver for the virtio-rng device on the qemu platform. The
> > device uses pci as a transport medium. The driver can be enabled with
> > the following configs
> >
> > CONFIG_VIRTIO
> > CONFIG_DM_RNG
> > CONFIG_VIRTIO_PCI
> > CONFIG_VIRTIO_RNG
> >
> > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
> > ---
> > Changes since V4:
> > * Return number of bytes read on a successful read, and a -ve value on
> >    error.
> >
> >   drivers/virtio/Kconfig         |  6 +++
> >   drivers/virtio/Makefile        |  1 +
> >   drivers/virtio/virtio-uclass.c |  1 +
> >   drivers/virtio/virtio_rng.c    | 85
> ++++++++++++++++++++++++++++++++++++++++++
> >   include/virtio.h               |  4 +-
> >   5 files changed, 96 insertions(+), 1 deletion(-)
> >   create mode 100644 drivers/virtio/virtio_rng.c
> >
>

<snip>


> > diff --git a/drivers/virtio/virtio_rng.c b/drivers/virtio/virtio_rng.c
> > new file mode 100644
> > index 0000000..fda8d04
> > --- /dev/null
> > +++ b/drivers/virtio/virtio_rng.c
> > @@ -0,0 +1,85 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Copyright (c) 2019, Linaro Limited
> > + */
> > +
> > +#include <common.h>
> > +#include <dm.h>
> > +#include <rng.h>
> > +#include <virtio_types.h>
> > +#include <virtio.h>
> > +#include <virtio_ring.h>
> > +
> > +struct virtio_rng_priv {
> > +     struct virtqueue *rng_vq;
> > +};
> > +
> > +static int virtio_rng_read(struct udevice *dev, void *data, size_t len)
> > +{
> > +     int ret;
> > +     unsigned int rsize = 0;
> > +     struct virtio_sg sg;
> > +     struct virtio_sg *sgs[1];
> > +     struct virtio_rng_priv *priv = dev_get_priv(dev);
> > +
> > +     /*
> > +      * Only INT_MAX number of bytes can be returned. If more
> > +      * bytes need to be read, the caller must do it in a loop.
> > +      */
> > +     if (len > INT_MAX)
> > +             len = INT_MAX;
> > +
> > +     sg.addr = data;
> > +     sg.length = len;
> > +     sgs[0] = &sg;
> > +
> > +     ret = virtqueue_add(priv->rng_vq, sgs, 0, 1);
> > +     if (ret)
> > +             return ret;
> > +
> > +     virtqueue_kick(priv->rng_vq);
> > +
> > +     while (!virtqueue_get_buf(priv->rng_vq, &rsize))
>
> This code assumes that data is 4 byte aligned and may lead to a crash
> due to missing alignment on ARM in function le32_to_cpu().
>

Are you referring to the virtqueue_get_buf function. Not sure I understand.
In any case, I will be sending an updated version which moves the loop into
the driver, as you had commented on my other patch.

-sughosh