Hi Laurent,
Thanks for the feedback.
> Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device API
>
> Hi Biju,
>
> On Wed, May 31, 2023 at 09:34:06AM +0000, Biju Das wrote:
> > > Subject: Re: [PATCH v5 01/11] i2c: Enhance i2c_new_ancillary_device
> > > API 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)??
>
> I don't see how there's a difference in behaviour in the code you have
> implemented, sorry.
Will reword,
Enhance i2c_new_ancillary_device() to instantiate a "I2C client device"
apart from the already supported "I2C dummy client device".
>
> > > > > > (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.
>
> The wording is better, but this is not what you have implemented in the
> code. The name doesn't select which parent is used.
It is the same implemented in the code.
For the existing users, aux_device_name is NULL --> The parent is set as "I2C adapter".
For instantiating a "i2c client device", aux_device_name is not NULL --> The parent is set as primary device.
The primary device is the one instantiated the "i2c client device" using
i2c_new_ancillary_device().
Please correct me if anything wrong here.
>
> > * 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;
>
> When called from i2c_new_ancillary_device(), __i2c_new_dummy_device() as
> a non-NULL parent argument. There is no change of behaviour *for
> i2c_new_dummy_device()*, but thre is a change of behaviour *for
> i2c_new_ancillary_device()*.
I don't think I understand what you mean.
For existing users, i2c_new_ancillary_device(..., aux_device_name=NULL) the behaviour is not changed.
Could you please elaborate further?
>
> > > > > 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??
>
> It's an I2C subsystem rule as far as I can tell. This is how it has been
> designed.
Wolfram/Geert:
Do you agree with Laurent's statement?
Cheers,
Biju
