Messages in this thread | | | Date | Tue, 1 Nov 2022 16:30:53 +0200 | From | Andy Shevchenko <> | Subject | Re: [PATCH v4 2/8] i2c: add I2C Address Translator (ATR) support |
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On Tue, Nov 01, 2022 at 03:20:26PM +0200, Tomi Valkeinen wrote: > From: Luca Ceresoli <luca@lucaceresoli.net> > > An ATR is a device that looks similar to an i2c-mux: it has an I2C > slave "upstream" port and N master "downstream" ports, and forwards > transactions from upstream to the appropriate downstream port. But is > is different in that the forwarded transaction has a different slave > address. The address used on the upstream bus is called the "alias" > and is (potentially) different from the physical slave address of the > downstream chip. > > Add a helper file (just like i2c-mux.c for a mux or switch) to allow > implementing ATR features in a device driver. The helper takes care or > adapter creation/destruction and translates addresses at each transaction.
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> i2c-topology > muxes/i2c-mux-gpio > i2c-sysfs > + muxes/i2c-atr
Doesn't make sense to group muxes/*, that they are following each other?
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> +I2C ADDRESS TRANSLATOR (ATR) > +M: Luca Ceresoli <luca@lucaceresoli.net>
Hmm... Are you going to maintain this? Or Review? Why not?
> +L: linux-i2c@vger.kernel.org > +S: Maintained > +F: drivers/i2c/i2c-atr.c > +F: include/linux/i2c-atr.h
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> + void *new_buf = kmalloc_array(num, sizeof(chan->orig_addrs[0]), > + GFP_KERNEL); > + if (new_buf == NULL) > + return -ENOMEM;
Isn't it better to write this as
void *new_buf;
new_buf = kmalloc_array(num, sizeof(chan->orig_addrs[0]), GFP_KERNEL); if (!new_buf) return -ENOMEM;
Remarks: - note the style of the conditional - why is it void?
Also, does it make sense to use krealloc_array() or is it complete replacement of the data?
> + kfree(chan->orig_addrs); > + chan->orig_addrs = new_buf; > + chan->orig_addrs_size = num;
...
> +static void i2c_atr_unmap_msgs(struct i2c_atr_chan *chan, struct i2c_msg msgs[], > + int num)
[] in the function parameter is longer than * and actually doesn't make difference in C. Ditto for the rest of similar cases.
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> +static int i2c_atr_smbus_xfer(struct i2c_adapter *adap, u16 addr, > + unsigned short flags, char read_write, u8 command, > + int size, union i2c_smbus_data *data)
Can flags be fixed size (yes I understand that in our case short would probably never be different to u16, but for the sake of clearness)?
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> +static int i2c_atr_attach_client(struct i2c_adapter *adapter, > + const struct i2c_board_info *info, > + const struct i2c_client *client) > +{ > + struct i2c_atr_chan *chan = adapter->algo_data; > + struct i2c_atr *atr = chan->atr; > + struct i2c_atr_cli2alias_pair *c2a;
> + u16 alias_id = 0;
Can we split assignment from the definition and locate it closer to the first use?
> + int ret = 0;
Useless assignment.
> + > + c2a = kzalloc(sizeof(*c2a), GFP_KERNEL); > + if (!c2a) > + return -ENOMEM; > + > + ret = atr->ops->attach_client(atr, chan->chan_id, info, client, > + &alias_id);
On one line looks better.
> + if (ret) > + goto err_free; > + if (alias_id == 0) { > + ret = -EINVAL; > + goto err_free; > + } > + > + c2a->client = client; > + c2a->alias = alias_id; > + list_add(&c2a->node, &chan->alias_list); > + > + return 0; > + > +err_free: > + kfree(c2a); > + return ret; > +}
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> +int i2c_atr_add_adapter(struct i2c_atr *atr, u32 chan_id, > + struct fwnode_handle *bus_handle) > +{ > + struct i2c_adapter *parent = atr->parent; > + struct device *dev = atr->dev; > + struct i2c_atr_chan *chan; > + char *symlink_name; > + int ret; > + > + if (chan_id >= atr->max_adapters) { > + dev_err(dev, "No room for more i2c-atr adapters\n"); > + return -EINVAL; > + } > + > + if (atr->adapter[chan_id]) { > + dev_err(dev, "Adapter %d already present\n", chan_id); > + return -EEXIST; > + } > + > + chan = kzalloc(sizeof(*chan), GFP_KERNEL); > + if (!chan) > + return -ENOMEM; > + > + chan->atr = atr; > + chan->chan_id = chan_id; > + INIT_LIST_HEAD(&chan->alias_list); > + mutex_init(&chan->orig_addrs_lock); > + > + snprintf(chan->adap.name, sizeof(chan->adap.name), "i2c-%d-atr-%d", > + i2c_adapter_id(parent), chan_id); > + chan->adap.owner = THIS_MODULE; > + chan->adap.algo = &atr->algo; > + chan->adap.algo_data = chan; > + chan->adap.dev.parent = dev; > + chan->adap.retries = parent->retries; > + chan->adap.timeout = parent->timeout; > + chan->adap.quirks = parent->quirks; > + chan->adap.lock_ops = &i2c_atr_lock_ops; > + chan->adap.attach_ops = &i2c_atr_attach_ops; > + > + if (bus_handle) { > + device_set_node(&chan->adap.dev, fwnode_handle_get(bus_handle)); > + } else { > + struct fwnode_handle *atr_node; > + struct fwnode_handle *child; > + u32 reg; > + > + atr_node = device_get_named_child_node(dev, "i2c-atr"); > + > + fwnode_for_each_child_node(atr_node, child) { > + ret = fwnode_property_read_u32(child, "reg", ®); > + if (ret) > + continue; > + if (chan_id == reg) > + break; > + } > + > + device_set_node(&chan->adap.dev, child); > + fwnode_handle_put(atr_node); > + }
It seems you have OF independent code, but by some reason you included of.h instead of property.h. Am I right?
> + ret = i2c_add_adapter(&chan->adap); > + if (ret) { > + dev_err(dev, "failed to add atr-adapter %u (error=%d)\n", > + chan_id, ret); > + goto err_add_adapter; > + } > + > + symlink_name = kasprintf(GFP_KERNEL, "channel-%u", chan_id);
No NULL check?
> + WARN(sysfs_create_link(&chan->adap.dev.kobj, &dev->kobj, "atr_device"), > + "can't create symlink to atr device\n"); > + WARN(sysfs_create_link(&dev->kobj, &chan->adap.dev.kobj, symlink_name), > + "can't create symlink for channel %u\n", chan_id);
Why WARNs? sysfs has already some in their implementation.
> + > + kfree(symlink_name); > + > + dev_dbg(dev, "Added ATR child bus %d\n", i2c_adapter_id(&chan->adap)); > + > + atr->adapter[chan_id] = &chan->adap; > + return 0; > + > +err_add_adapter: > + mutex_destroy(&chan->orig_addrs_lock); > + kfree(chan); > + return ret; > +}
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> + struct fwnode_handle *fwnode = adap->dev.fwnode;
Please don't dereference fwnode like this, we have dev_fwnode() for that.
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> + if (atr->adapter[chan_id] == NULL) {
!
> + dev_err(dev, "Adapter %d does not exist\n", chan_id); > + return; > + }
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> + snprintf(symlink_name, sizeof(symlink_name), > + "channel-%u", chan->chan_id);
Once line?
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> + atr_size = struct_size(atr, adapter, max_adapters);
> + if (atr_size == SIZE_MAX) > + return ERR_PTR(-EOVERFLOW);
Dunno if you really need this to be separated from devm_kzalloc(), either way you will get an error, but in embedded case it will be -ENOMEM.
> + atr = devm_kzalloc(dev, atr_size, GFP_KERNEL); > + if (!atr) > + return ERR_PTR(-ENOMEM);
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> +EXPORT_SYMBOL_GPL(i2c_atr_delete);
I would put these to their own namespace from day 1.
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> +/** > + * Helper to add I2C ATR features to a device driver. > + */
??? Copy'n'paste typo?
> +struct i2c_atr { > + /* private: internal use only */ > + > + struct i2c_adapter *parent; > + struct device *dev; > + const struct i2c_atr_ops *ops; > + > + void *priv; > + > + struct i2c_algorithm algo; > + struct mutex lock; > + int max_adapters; > + > + struct i2c_adapter *adapter[0];
No VLAs.
> +};
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> +int i2c_atr_add_adapter(struct i2c_atr *atr, u32 chan_id, > + struct fwnode_handle *bus_np);
Missing
struct fwnode_handle;
at the top of the file?
-- With Best Regards, Andy Shevchenko
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