Re: [PATCH V2 4/6] tools/vhost-user-i2c: Add backend driver

["Alex Bennée" <alex.bennee@linaro.org>]

Viresh Kumar <viresh.kumar@linaro.org> writes:

> This adds the vhost-user backend driver to support virtio based I2C and
> SMBUS devices.
>
> vhost-user-i2c --help
>
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
<snip>
> +
> +static VI2cAdapter *vi2c_create_adapter(int32_t bus, uint16_t client_addr[],
> +                                        int32_t n_client)
> +{
> +    VI2cAdapter *adapter;
> +    char path[20];

If you use:

    g_autofree char *path = NULL;

If fact you could also use g_autofree with adapter to make you exit case
a little easier.

> +    uint64_t funcs;
> +    int32_t fd, i;
> +
> +    if (bus < 0) {
> +        return NULL;
> +    }
> +
> +    adapter = g_malloc0(sizeof(*adapter));

g_malloc will abort() on lack of memory so you can skip the check here.

> +    if (!adapter) {
> +        g_printerr("failed to alloc adapter");
> +        return NULL;
> +    }
> +
> +    snprintf(path, sizeof(path), "/dev/i2c-%d", bus);
> +    path[sizeof(path) - 1] = '\0';

then this becomes:

  path = g_strdup_printf("/dev/i2c-%d", bus);

> +
> +    fd = open(path, O_RDWR);
> +    if (fd < 0) {
> +        g_printerr("virtio_i2c: failed to open %s\n", path);
> +        goto fail;
> +    }
> +
> +    adapter->fd = fd;
> +    adapter->bus = bus;
> +
> +    if (ioctl(fd, I2C_FUNCS, &funcs) < 0) {
> +        g_printerr("virtio_i2c: failed to get functionality %s: %d\n", path,
> +                   errno);
> +        goto close_fd;
> +    }
> +
> +    if (funcs & I2C_FUNC_I2C) {
> +        adapter->smbus = false;
> +    } else if (funcs & I2C_FUNC_SMBUS_WORD_DATA) {
> +        adapter->smbus = true;
> +    } else {
> +        g_printerr("virtio_i2c: invalid functionality %lx\n", funcs);
> +        goto close_fd;
> +    }
> +
> +    for (i = 0; i < n_client; i++) {
> +        if (client_addr[i]) {
> +            if (!vi2c_set_client_addr(adapter, client_addr[i])) {
> +                goto close_fd;
> +            }
> +
> +            if (adapter->clients[client_addr[i]]) {
> +                g_printerr("client addr 0x%x repeat, not allowed.\n",
> +                           client_addr[i]);
> +                goto close_fd;
> +            }
> +
> +            adapter->clients[client_addr[i]] = true;
> +            if (verbose) {
> +                g_print("Added client 0x%x to bus %u\n", client_addr[i], bus);
> +            }
> +        }
> +    }
> +
> +    if (verbose) {
> +        g_print("Added adapter: bus: %d, func %s\n", bus,
> +                adapter->smbus ? "smbus" : "i2c");
> +    }
> +    return adapter;

This would then be:

  return g_steal_pointer(adapter);

> +
> +close_fd:
> +    close(fd);
> +fail:
> +    g_free(adapter);
> +    return NULL;
> +}
> +
> +/*
> + * Virtio I2C device list format.
> + *
> + * <bus>:<client_addr>[:<client_addr>],
> + * [<bus>:<client_addr>[:<client_addr>]]
> + *
> + * bus (dec): adatper bus number.
> + *     e.g. 2 for /dev/i2c-2
> + * client_addr (hex): address for client device
> + *     e.g. 0x1C or 1C
> + *
> + * Example: --device-list="2:0x1c:0x20,3:0x10:0x2c"
> + *
> + * Note: client address can not repeat.
> + */
> +static int32_t vi2c_parse(VuI2c *i2c)
> +{
> +    uint16_t client_addr[MAX_I2C_VDEV];
> +    int32_t n_adapter = 0, n_client;
> +    int64_t addr, bus;
> +    const char *cp, *t;
> +
> +    while (device_list) {
> +        /* Read <bus>:<client_addr>[:<client_addr>] entries one by one */
> +        cp = strsep(&device_list, ",");

The glib approach would be to use g_strsplit(device_list, ",", 0) which
you can then iterate over with something like:

    for (i = 0; cp[i] != NULL; i++) {

    } 

    g_strfreev(cp);

> +
> +        if (!cp || *cp == '\0') {
> +            break;
> +        }
> +
> +        if (n_adapter == MAX_I2C_ADAPTER) {
> +            g_printerr("too many adapter (%d), only support %d\n", n_adapter,
> +                       MAX_I2C_ADAPTER);
> +            goto out;
> +        }
> +
> +        if (qemu_strtol(cp, &t, 10, &bus) || bus < 0) {
> +            g_printerr("Invalid bus number %s\n", cp);
> +            goto out;
> +        }
> +
> +        cp = t;
> +        n_client = 0;
> +
> +        /* Parse clients <client_addr>[:<client_addr>] entries one by
> one */

Then this would be:

     **dev = g_strsplit(cp[i], ":", 2);
     if (dev && dev[0]) {

         if (dev[1]) {
         }
     }
     g_freestrv(dev);

which would avoid you manually iterating over the string.

> +        while (cp != NULL && *cp != '\0') {
> +            if (*cp == ':') {
> +                cp++;
> +            }
> +
> +            if (n_client == MAX_I2C_VDEV) {
> +                g_printerr("too many devices (%d), only support %d\n",
> +                           n_client, MAX_I2C_VDEV);
> +                goto out;
> +            }
> +
> +            if (qemu_strtol(cp, &t, 16, &addr) ||
> +                addr < 0 || addr > MAX_I2C_VDEV) {
> +                g_printerr("Invalid address %s : %lx\n", cp, addr);
> +                goto out;
> +            }
> +
> +            client_addr[n_client++] = addr;
> +            cp = t;
> +            if (verbose) {
> +                g_print("i2c adapter %ld:0x%lx\n", bus, addr);
> +            }
> +        }
> +
> +        i2c->adapter[n_adapter] = vi2c_create_adapter(bus, client_addr,
> +                                                      n_client);
> +        if (!i2c->adapter[n_adapter]) {
> +            goto out;
> +        }
> +
> +        n_adapter++;
> +    }
> +
> +    if (!n_adapter) {
> +        g_printerr("Failed to add any adapters\n");
> +        return -1;
> +    }
> +
> +    i2c->adapter_num = n_adapter;
> +
> +    if (!vi2c_map_adapters(i2c)) {
> +        return 0;
> +    }
> +
> +out:
> +    vi2c_remove_adapters(i2c);
> +    return -1;
> +}
> +
<snip>
> +
> +static void vi2c_handle_ctrl(VuDev *dev, int qidx)
> +{
> +    VuVirtq *vq = vu_get_queue(dev, qidx);
> +    struct virtio_i2c_out_hdr *out_hdr;
> +    size_t i, count = 0, len, in_hdr_len;
> +    struct i2c_msg *msgs;
> +    VuVirtqElement *elem;
> +    uint8_t status;
> +    struct {
> +        struct virtio_i2c_in_hdr *in_hdr;
> +        VuVirtqElement *elem;
> +        size_t size;
> +    } *info;
> +
> +    /* Count number of messages */
> +    do {
> +        elem = vu_queue_pop(dev, vq, sizeof(VuVirtqElement));
> +    } while (elem && ++count);

Can you expand on this comment as to why we can't process each message
as we come to it?

> +
> +    if (!count) {
> +        if (verbose) {
> +            g_printerr("Virtqueue can't have 0 elements\n");
> +        }
> +        return;
> +    }
> +
> +    /* Rewind everything, now that we have counted the number of messages */
> +    vu_queue_rewind(dev, vq, count);
> +
> +    if (verbose) {
> +        g_print("Received %ld messages in virtqueue\n", count);
> +    }
> +
> +    /* Allocate memory for msgs and info */
> +    msgs = g_malloc0_n(count, sizeof(*msgs) + sizeof(*info));
> +    if (!msgs) {
> +        g_printerr("failed to allocate space for messages\n");
> +        return;
> +    }

g_malloc0_n will abort() or succeed. Could this be a g_new and be typed
in some way?

> +    info = (void *)(msgs + count);
> +
> +    for (i = 0; i < count; i++) {
> +        elem = vu_queue_pop(dev, vq, sizeof(VuVirtqElement));
> +        if (!elem) {
> +            g_printerr("Failed to pop element: %ld : %ld\n", i, count);
> +            goto out;
> +        }

not withstanding the above comment this seems like an assert() because
it should never fail?

> +        info[i].elem = elem;
> +        info[i].size = sizeof(*info[i].in_hdr);
> +
> +        g_debug("%s: got queue (in %d, out %d)", __func__, elem->in_num,
> +                elem->out_num);
> +
> +        /* Validate size of "out" header */
> +        if (elem->out_sg[0].iov_len != sizeof(*out_hdr)) {
> +            g_warning("%s: Invalid out hdr %zu : %zu\n", __func__,
> +                      elem->out_sg[0].iov_len, sizeof(*out_hdr));
> +            goto out;
> +        }
> +
> +        out_hdr = elem->out_sg[0].iov_base;
> +
> +        /* Bit 0 is reserved in virtio spec */
> +        msgs[i].addr = le16toh(out_hdr->addr) >> 1;
> +
> +        /* Read Operation */
> +        if (elem->out_num == 1 && elem->in_num == 2) {
> +            len = elem->in_sg[0].iov_len;
> +            if (!len) {
> +                g_warning("%s: Read buffer length can't be zero\n", __func__);
> +                goto out;
> +            }
> +
> +            msgs[i].buf = elem->in_sg[0].iov_base;
> +            msgs[i].flags = I2C_M_RD;
> +            msgs[i].len = len;
> +
> +            info[i].in_hdr = elem->in_sg[1].iov_base;
> +            info[i].size += len;
> +            in_hdr_len = elem->in_sg[1].iov_len;
> +        } else if (elem->out_num == 2 && elem->in_num == 1) {
> +            /* Write Operation */
> +            len = elem->out_sg[1].iov_len;
> +            if (!len) {
> +                g_warning("%s: Write buffer length can't be zero\n", __func__);
> +                goto out;
> +            }
> +
> +            msgs[i].buf = elem->out_sg[1].iov_base;
> +            msgs[i].flags = 0;
> +            msgs[i].len = len;
> +
> +            info[i].in_hdr = elem->in_sg[0].iov_base;
> +            in_hdr_len = elem->in_sg[0].iov_len;
> +        } else {
> +            g_warning("%s: Transfer type not supported (in %d, out %d)\n",
> +                      __func__, elem->in_num, elem->out_num);
> +            goto out;
> +        }
> +
> +        /* Validate size of "in" header */
> +        if (in_hdr_len != sizeof(*(info[i].in_hdr))) {
> +            g_warning("%s: Invalid in hdr %zu : %zu\n", __func__, in_hdr_len,
> +                      sizeof(*(info[i].in_hdr)));
> +            goto out;
> +        }
> +    }
> +
> +    status = vi2c_xfer(dev, msgs, count);
> +
> +    for (i = 0; i < count; i++) {
> +        info[i].in_hdr->status = status;
> +        vu_queue_push(dev, vq, info[i].elem, info[i].size);
> +    }
> +
> +    vu_queue_notify(dev, vq);
> +
> +out:
> +    g_free(msgs);
> +}
> +
<snip>
> diff --git a/tools/vhost-user-i2c/meson.build b/tools/vhost-user-i2c/meson.build
> new file mode 100644
> index 000000000000..f71e9fec7df6
> --- /dev/null
> +++ b/tools/vhost-user-i2c/meson.build
> @@ -0,0 +1,10 @@
> +executable('vhost-user-i2c', files(
> +  'main.c'),
> +  dependencies: [qemuutil, glib, gio],
> +  install: true,
> +  install_dir: get_option('libexecdir'))
> +
> +configure_file(input: '50-qemu-i2c.json.in',
> +               output: '50-qemu-i2c.json',
> +               configuration: config_host,

FYI this now needs to be:

               configuration: { 'libexecdir' : get_option('prefix') / get_option('libexecdir') },

to properly pass libexecdir above.

> +               install_dir: qemu_datadir / 'vhost-user')


-- 
Alex Bennée