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

[Viresh Kumar]

On 02-04-21, 10:55, Jie Deng wrote:
> 
> On 2021/4/1 20:12, Viresh Kumar wrote:
> > +
> > +/* vhost-user-i2c definitions */
> > +
> > +#define MAX_I2C_VDEV                    (1 << 7)
> > +#define MAX_I2C_ADAPTER                 16
> 
> Generally speaking, 16 is big enough for most cases. But comparing with
> static configuration,
> I think it is better if we can check how many adapters in the host when
> doing initialization and
> use that number as "MAX_I2C_ADAPTER".

Hmm, so this doesn't limit the adapter number in /dev/i2cX (i.e. we can still
process /dev/i2c99), but rather how many adapters we can pass in
--device-list="" parameter. And so I feel 16 is big enough and if someone really
needs more, then they can update the macro here.

> > +static VI2cAdapter *vi2c_create_adapter(int32_t bus, uint16_t 
> > client_addr[],
> > +                                        int32_t n_client)
> > +{
> > +    VI2cAdapter *adapter;
> > +    char path[20];
> > +    uint64_t funcs;
> > +    int32_t fd, i;
> > +
> > +    if (bus < 0) {
> > +        return NULL;
> > +    }
> > +
> > +    adapter = g_malloc0(sizeof(*adapter));
> > +    if (!adapter) {
> > +        g_printerr("failed to alloc adapter");
> > +        return NULL;
> > +    }
> > +
> > +    snprintf(path, sizeof(path), "/dev/i2c-%d", bus);
> > +    path[sizeof(path) - 1] = '\0';
> > +
> > +    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) {
> 
> 
> Only I2C_FUNC_SMBUS_WORD_DATA is checked here. But in addition to it, the
> smbus_xfer
> seems support I2C_FUNC_SMBUS_BYTE, I2C_FUNC_SMBUS_BYTE_DATA. So if an
> adapter only
> support the latter two, it will never go to smbus_xfer.

Yeah, I missed it. Thanks. I am updating it as:

-    } else if (funcs & I2C_FUNC_SMBUS_WORD_DATA) {
+    } else if (funcs & (I2C_FUNC_SMBUS_WORD_DATA | I2C_FUNC_SMBUS_BYTE |
+                        I2C_FUNC_SMBUS_BYTE_DATA)) {

-- 
viresh