Hi Laurent,
Thanks for the feedback.
> Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
>
> Hi Biju,
>
> On Mon, May 29, 2023 at 09:00:43AM +0000, Biju Das wrote:
> > > Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device
> > > API On Mon, May 22, 2023 at 11:18:39AM +0100, Biju Das wrote:
> > > > Renesas PMIC RAA215300 exposes two separate i2c devices, one for
> > > > the main device and another for rtc device.
> > > >
> > > > Enhance i2c_new_ancillary_device() to instantiate a real device.
> > >
> > > Doesn't it already instantiate a real device ?
> >
> And that function calls i2c_new_client_device(), which allocates a
> struct i2c_client that embeds a struct device, and registers that device
> with the kernel device core. How is that different, in terms of
> instantiating a "real device", from what this patch does ?
There is a difference, right? it instantiates new "i2c dummy client" driver and
a "real i2c client device" driver like rtc device client(rtc-isl2108)??
>
> > > > (eg: Instantiate rtc device from PMIC driver)
> > > >
> > > > Added helper function __i2c_new_dummy_device to share the code
> > > > between i2c_new_dummy_device and i2c_new_ancillary_device().
> > > >
> > > > Also added helper function __i2c_new_client_device() to pass
> > > > parent dev parameter, so that the ancillary device can assign its
> > > > parent during creation.
> > > >
> > > > Suggested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> > > > Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > > > ---
> > > > v4->v5:
> > > > * Replaced parameter dev->parent in __i2c_new_client_device() and
> > > > __i2c_new_dummy_device().
> > > > * Improved error message in __i2c_new_dummy_device() by printing
> device name.
> > > > * Updated comment for ancillary's device parent
> > > > * Dropped aux_device_name check in i2c_new_ancillary_device().
> > > > v3->v4:
> > > > * Dropped Rb tag from Geert as there are new changes.
> > > > * Introduced __i2c_new_dummy_device() to share the code between
> > > > i2c_new_dummy_device and i2c_new_ancillary_device().
> > > > * Introduced __i2c_new_client_device() to pass parent dev
> > > > parameter, so that the ancillary device can assign its parent
> during
> > > > creation.
> > > > v3:
> > > > * New patch
> > > >
> > > > Ref:
> > > >
> > > > ---
> > > > drivers/gpu/drm/bridge/adv7511/adv7511_drv.c | 6 +-
> > > > drivers/i2c/i2c-core-base.c | 92 +++++++++++++--
> ----
> > > -
> > > > drivers/media/i2c/adv748x/adv748x-core.c | 2 +-
> > > > drivers/media/i2c/adv7604.c | 3 +-
> > > > include/linux/i2c.h | 3 +-
> > > > 5 files changed, 69 insertions(+), 37 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > index ddceafa7b637..86306b010a0a 100644
> > > > --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > > @@ -1072,7 +1072,7 @@ static int adv7511_init_cec_regmap(struct
> adv7511 *adv)
> > > > int ret;
> > > >
> > > > adv->i2c_cec = i2c_new_ancillary_device(adv->i2c_main,
> "cec",
> > > > - ADV7511_CEC_I2C_ADDR_DEFAULT);
> > > > + ADV7511_CEC_I2C_ADDR_DEFAULT, NULL);
> > > > if (IS_ERR(adv->i2c_cec))
> > > > return PTR_ERR(adv->i2c_cec);
> > > >
> > > > @@ -1261,7 +1261,7 @@ static int adv7511_probe(struct i2c_client
> *i2c)
> > > > adv7511_packet_disable(adv7511, 0xffff);
> > > >
> > > > adv7511->i2c_edid = i2c_new_ancillary_device(i2c, "edid",
> > > > - ADV7511_EDID_I2C_ADDR_DEFAULT);
> > > > + ADV7511_EDID_I2C_ADDR_DEFAULT,
> NULL);
> > > > if (IS_ERR(adv7511->i2c_edid)) {
> > > > ret = PTR_ERR(adv7511->i2c_edid);
> > > > goto uninit_regulators;
> > > > @@ -1271,7 +1271,7 @@ static int adv7511_probe(struct i2c_client
> *i2c)
> > > > adv7511->i2c_edid->addr << 1);
> > > >
> > > > adv7511->i2c_packet = i2c_new_ancillary_device(i2c,
> "packet",
> > > > - ADV7511_PACKET_I2C_ADDR_DEFAULT);
> > > > + ADV7511_PACKET_I2C_ADDR_DEFAULT,
> NULL);
> > > > if (IS_ERR(adv7511->i2c_packet)) {
> > > > ret = PTR_ERR(adv7511->i2c_packet);
> > > > goto err_i2c_unregister_edid;
> > > > diff --git a/drivers/i2c/i2c-core-base.c
> > > > b/drivers/i2c/i2c-core-base.c index ae3af738b03f..3442aa80290f
> > > > 100644
> > > > --- a/drivers/i2c/i2c-core-base.cvvccc
> > > > +++ b/drivers/i2c/i2c-core-base.cckvlrgnulkj
> > > > @@ -893,24 +893,10 @@ int i2c_dev_irq_from_resources(const struct
> resource *resources,
> > > > return 0;
> > > > }
> > > >
> > > > -/**
> > > > - * i2c_new_client_device - instantiate an i2c device
> > > > - * @adap: the adapter managing the device
> > > > - * @info: describes one I2C device; bus_num is ignored
> > > > - * Context: can sleep
> > > > - *
> > > > - * Create an i2c device. Binding is handled through driver model
> > > > - * probe()/remove() methods. A driver may be bound to this
> > > > device when we
> > > > - * return from this function, or any later moment (e.g. maybe
> > > > hotplugging will
> > > > - * load the driver module). This call is not appropriate for use
> > > > by mainboard
> > > > - * initialization logic, which usually runs during an
> > > > arch_initcall() long
> > > > - * before any i2c_adapter could exist.
> > > > - *
> > > > - * This returns the new i2c client, which may be saved for later
> > > > use with
> > > > - * i2c_unregister_device(); or an ERR_PTR to describe the error.
> > > > - */
> > > > -struct i2c_client *
> > > > -i2c_new_client_device(struct i2c_adapter *adap, struct
> > > > i2c_board_info const *info)
> > > > +static struct i2c_client *
> > > > +__i2c_new_client_device(struct i2c_adapter *adap,
> > > > + struct i2c_board_info const *info,
> > > > + struct device *parent)
> > > > {
> > > > struct i2c_client *client;
> > > > int status;
> > > > @@ -944,7 +930,7 @@ i2c_new_client_device(struct i2c_adapter
> *adap, struct i2c_board_info const *inf
> > > > if (status)
> > > > goto out_err;
> > > >
> > > > - client->dev.parent = &client->adapter->dev;
> > > > + client->dev.parent = parent ? parent : &client->adapter-
> >dev;
> > > > client->dev.bus = &i2c_bus_type;
> > > > client->dev.type = &i2c_client_type;
> > > > client->dev.of_node = of_node_get(info->of_node); @@ -984,6
> > > > +970,28 @@ i2c_new_client_device(struct i2c_adapter *adap, struct
> i2c_board_info const *inf
> > > > kfree(client);
> > > > return ERR_PTR(status);
> > > > }
> > > > +
> > > > +/**
> > > > + * i2c_new_client_device - instantiate an i2c device
> > > > + * @adap: the adapter managing the device
> > > > + * @info: describes one I2C device; bus_num is ignored
> > > > + * Context: can sleep
> > > > + *
> > > > + * Create an i2c device. Binding is handled through driver model
> > > > + * probe()/remove() methods. A driver may be bound to this
> > > > +device when we
> > > > + * return from this function, or any later moment (e.g. maybe
> > > > +hotplugging will
> > > > + * load the driver module). This call is not appropriate for use
> > > > +by mainboard
> > > > + * initialization logic, which usually runs during an
> > > > +arch_initcall() long
> > > > + * before any i2c_adapter could exist.
> > > > + *
> > > > + * This returns the new i2c client, which may be saved for later
> > > > +use with
> > > > + * i2c_unregister_device(); or an ERR_PTR to describe the error.
> > > > + */
> > > > +struct i2c_client *
> > > > +i2c_new_client_device(struct i2c_adapter *adap, struct
> > > > +i2c_board_info const *info) {
> > > > + return __i2c_new_client_device(adap, info, NULL); }
> > > > EXPORT_SYMBOL_GPL(i2c_new_client_device);
> > > >
> > > > /**
> > > > @@ -1054,6 +1062,26 @@ static struct i2c_driver dummy_driver = {
> > > > .id_table = dummy_id,
> > > > };
> > > >
> > > > +static struct i2c_client *__i2c_new_dummy_device(struct
> i2c_adapter *adapter,
> > > > + u16 address, const char
> *name,
> > > > + struct device *parent)
> > > > +{
> > > > + struct i2c_board_info info = {
> > > > + I2C_BOARD_INFO("dummy", address),
> > > > + };
> > > > +
> > > > + if (name) {
> > > > + ssize_t ret = strscpy(info.type, name,
> sizeof(info.type));
> > > > +
> > > > + if (ret < 0)
> > > > + return ERR_PTR(dev_err_probe(&adapter->dev, ret,
> > > > + "Invalid device name:
> %s\n",
> > > > + name));
> > > > + }
> > > > +
> > > > + return __i2c_new_client_device(adapter, &info, parent); }
> > > > +
> > > > /**
> > > > * i2c_new_dummy_device - return a new i2c device bound to a
> dummy driver
> > > > * @adapter: the adapter managing the device @@ -1074,11 +1102,7
> > > > @@ static struct i2c_driver dummy_driver = {
> > > > */
> > > > struct i2c_client *i2c_new_dummy_device(struct i2c_adapter
> > > > *adapter,
> > > > u16 address) {
> > > > - struct i2c_board_info info = {
> > > > - I2C_BOARD_INFO("dummy", address),
> > > > - };
> > > > -
> > > > - return i2c_new_client_device(adapter, &info);
> > > > + return __i2c_new_dummy_device(adapter, address, NULL, NULL);
> > > > }
> > > > EXPORT_SYMBOL_GPL(i2c_new_dummy_device);
> > > >
> > > > @@ -1122,15 +1146,19 @@
> EXPORT_SYMBOL_GPL(devm_i2c_new_dummy_device);
> > > > * @client: Handle to the primary client
> > > > * @name: Handle to specify which secondary address to get
> > > > * @default_addr: Used as a fallback if no secondary address was
> > > > specified
> > > > + * @aux_device_name: Ancillary device name
> > > > * Context: can sleep
> > > > *
> > > > * I2C clients can be composed of multiple I2C slaves bound
> together in a single
> > > > * component. The I2C client driver then binds to the master I2C
> > > > slave and needs
> > > > - * to create I2C dummy clients to communicate with all the other
> slaves.
> > > > + * to create I2C ancillary clients to communicate with all the
> other slaves.
> > > > *
> > > > - * This function creates and returns an I2C dummy client whose
> > > > I2C address is
> > > > - * retrieved from the platform firmware based on the given slave
> > > > name. If no
> > > > - * address is specified by the firmware default_addr is used.
> > > > + * This function creates and returns an I2C ancillary client
> > > > + whose I2C address
> > > > + * is retrieved from the platform firmware based on the given
> > > > + slave name. if
> > > > + * aux_device_name is specified by the firmware,
> > >
> > > Unless I'm missing something, aux_device_name isn't specified by the
> > > firmware, it's a function parameter.
> >
> > It is specified in the platform firmware(device tree firmware).
>
> What I meant, in the context of the documentation here, is that the
> address is retrieved from the platform firmware by the
> i2c_new_ancillary_device() function, not passed as a parameter, while
> the name is passed as a parameter. It's not relevant, for the
> documentation of this function, where the caller gets the name from.
Are you ok with these wordings?
* This function creates and returns an I2C ancillary client whose I2C address
* is retrieved from the platform firmware based on the given slave name. If
* aux_device_name is not NULL, the ancillary's device parent
* will be set to the primary device otherwise it will be set to I2C adapter.
* If no address is specified by the firmware default_addr is used.
>
> > > > the ancillary's device parent
> > > > + * will be set to the primary device.
> > >
> > > This doesn't seem to match the implementation. With this patch the
> > > ancillary device's parent is always the primary device. Are you sure
> > > this won't cause any regression ?
> >
> > There is no regression as existing users only instantiate dummy
> device.
>
> Sorry, I don't follow you here. Existing callers of
> i2c_new_ancillary_device() today get an i2c_client device whose parent
> is the I2C adapter. With this patch they will get an i2c_client device
> whose parent is the main i2c_client. That's a change in behaviour, which
> could cause all sorts of issues.
Please see the patch snippet below, there is no regression.
client->dev.parent = parent ? parent : &client->adapter->dev;
>
> > > And why do you need this ?
> >
> > As per Krzysztof [2],
> >
> > The DT schema allows multiple addresses for children. But we lack
> > implementation of parent child relationship, As parent owns the
> resources.
> > Child device needs to parse parent node to get some resource like
> > clocks.
> >
> > [2]
>
> The I2C ancillary clients are not meant to be handled by separate
> drivers.
Is it a Linux rule??
>You're supposed to have one device node in DT, which causes the
> I2C core to instantiate a main i2c_client, and bind it to one driver.
> That driver then uses i2c_new_ancillary_device() to create other
> i2c_client instances for the secondary I2C addresses. Those i2c_client
> instances are not bound to a separate driver,
Wolfram/Geert, Is it limitation from i2c?
Cheers,
Biju
> so there should be no code
> that needs to look at the parent for resources.
>
> > > > If no address is specified by the firmware
> > > > + * default_addr is used. If no aux_device_name is specified by
> > > > + the firmware, it
> > >
> > > Same here regarding firmware.
> > >
> > > > + * will create an I2C dummy client.
> > > > *
> > > > * On DT-based platforms the address is retrieved from the "reg"
> property entry
> > > > * cell whose "reg-names" value matches the slave name.
> > > > @@ -1139,8 +1167,9 @@
> EXPORT_SYMBOL_GPL(devm_i2c_new_dummy_device);
> > > > * i2c_unregister_device(); or an ERR_PTR to describe the error.
> > > > */
> > > > struct i2c_client *i2c_new_ancillary_device(struct i2c_client
> *client,
> > > > - const char *name,
> > > > - u16 default_addr)
> > > > + const char *name,
> > > > + u16 default_addr,
> > > > + const char *aux_device_name)
> > > > {
> > > > struct device_node *np = client->dev.of_node;
> > > > u32 addr = default_addr;
> > > > @@ -1153,7 +1182,8 @@ struct i2c_client
> *i2c_new_ancillary_device(struct i2c_client *client,
> > > > }
> > > >
> > > > dev_dbg(&client->adapter->dev, "Address for %s : 0x%x\n",
> name, addr);
> > > > - return i2c_new_dummy_device(client->adapter, addr);
> > > > + return __i2c_new_dummy_device(client->adapter, addr,
> aux_device_name,
> > > > + &client->dev);
> > > > }
> > > > EXPORT_SYMBOL_GPL(i2c_new_ancillary_device);
> > > >
> > > > diff --git a/drivers/media/i2c/adv748x/adv748x-core.c
> > > > b/drivers/media/i2c/adv748x/adv748x-core.c
> > > > index 4498d78a2357..5bdf7b0c6bf3 100644
> > > > --- a/drivers/media/i2c/adv748x/adv748x-core.c
> > > > +++ b/drivers/media/i2c/adv748x/adv748x-core.c
> > > > @@ -186,7 +186,7 @@ static int adv748x_initialise_clients(struct
> > > adv748x_state *state)
> > > > state->i2c_clients[i] = i2c_new_ancillary_device(
> > > > state->client,
> > > > adv748x_default_addresses[i].name,
> > > > -
> adv748x_default_addresses[i].default_addr);
> > > > + adv748x_default_addresses[i].default_addr,
> > > NULL);
> > > >
> > > > if (IS_ERR(state->i2c_clients[i])) {
> > > > adv_err(state, "failed to create i2c client
> %u\n", i);
> > > diff --git
> > > > a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c index
> > > > 3d0898c4175e..63fa44c9d27c 100644
> > > > --- a/drivers/media/i2c/adv7604.c
> > > > +++ b/drivers/media/i2c/adv7604.c
> > > > @@ -2935,7 +2935,8 @@ static struct i2c_client
> > > *adv76xx_dummy_client(struct v4l2_subdev *sd,
> > > > else
> > > > new_client = i2c_new_ancillary_device(client,
> > > > adv76xx_default_addresses[page].name,
> > > > -
> adv76xx_default_addresses[page].default_addr);
> > > > +
> adv76xx_default_addresses[page].default_addr,
> > > > + NULL);
> > > >
> > > > if (!IS_ERR(new_client))
> > > > io_write(sd, io_reg, new_client->addr << 1); diff --
> git
> > > > a/include/linux/i2c.h b/include/linux/i2c.h index
> > > > 13a1ce38cb0c..0ce344724209 100644
> > > > --- a/include/linux/i2c.h
> > > > +++ b/include/linux/i2c.h
> > > > @@ -489,7 +489,8 @@ devm_i2c_new_dummy_device(struct device *dev,
> > > > struct i2c_adapter *adap, u16 addr struct i2c_client *
> > > > i2c_new_ancillary_device(struct i2c_client *client,
> > > > const char *name,
> > > > - u16 default_addr);
> > > > + u16 default_addr,
> > > > + const char *aux_device_name);
> > > >
> > > > void i2c_unregister_device(struct i2c_client *client);
> > > >
>
> --
> Regards,
>
> Laurent Pinchart
