[v4,1/2] dm: core: add function uclass_probe_all() to probe all devices

From: Vabhav Sharma <vabhav.sharma@nxp.com>

Support a common method to probe all devices associated with uclass.

This includes data structures and code for finding the first device and
looping for remaining devices associated with uclasses (groups of devices
with the same purpose, e.g. all SERIAL ports will be in the same uclass).

An example is SBSA compliant PL011 UART IP, where firmware does the serial
port initialization and prepare uart device to let the kernel use it for
sending and reveiving the characters.SERIAL uclass will use this function
to initialize PL011 UART ports.

The feature is enabled with CONFIG_DM.

Signed-off-by: Vabhav Sharma <vabhav.sharma@nxp.com>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
--
  v4:
  Incorporated review comments of Simon
  Removed if (dev)..  conditional check

  v3:
  Incorporated review comments of Stephan,Simon
  Related discussion https://patchwork.ozlabs.org/project/uboot/patch/1601400
385-11854-1-git-send-email-vabhav.sharma@oss.nxp.com/
---
 drivers/core/uclass.c | 16 ++++++++++++++++
 include/dm/uclass.h   | 12 ++++++++++++
 2 files changed, 28 insertions(+)

On 11/17/20 10:00 AM, Vabhav Sharma wrote:
> From: Vabhav Sharma <vabhav.sharma@nxp.com>
> 
> Support a common method to probe all devices associated with uclass.
> 
> This includes data structures and code for finding the first device and
> looping for remaining devices associated with uclasses (groups of devices
> with the same purpose, e.g. all SERIAL ports will be in the same uclass).
> 
> An example is SBSA compliant PL011 UART IP, where firmware does the serial
> port initialization and prepare uart device to let the kernel use it for
> sending and reveiving the characters.SERIAL uclass will use this function
> to initialize PL011 UART ports.
> 
> The feature is enabled with CONFIG_DM.
> 
> Signed-off-by: Vabhav Sharma <vabhav.sharma@nxp.com>
> Reviewed-by: Stefan Roese <sr@denx.de>
> Reviewed-by: Simon Glass <sjg@chromium.org>
> --
>   v4:
>   Incorporated review comments of Simon
>   Removed if (dev)..  conditional check
> 
>   v3:
>   Incorporated review comments of Stephan,Simon
>   Related discussion https://patchwork.ozlabs.org/project/uboot/patch/1601400
> 385-11854-1-git-send-email-vabhav.sharma@oss.nxp.com/
> ---
>  drivers/core/uclass.c | 16 ++++++++++++++++
>  include/dm/uclass.h   | 12 ++++++++++++
>  2 files changed, 28 insertions(+)
> 
> diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c
> index c3f1b73..a1dc8bb 100644
> --- a/drivers/core/uclass.c
> +++ b/drivers/core/uclass.c
> @@ -792,6 +792,22 @@ int uclass_pre_remove_device(struct udevice *dev)
>  }
>  #endif
>  
> +int uclass_probe_all(enum uclass_id id)
> +{
> +	struct udevice *dev;
> +	int ret;
> +
> +	ret = uclass_first_device(id, &dev);
> +	if (ret || !dev)
> +		return ret;
> +
> +	/* Scanning uclass to probe all devices */
> +	for (; dev; uclass_next_device(&dev))

You must check the return value of this function.

Also, I would suggest using a while loop instead of an empty for loop.

> +		;
> +
> +	return 0;
> +}
> +
>  UCLASS_DRIVER(nop) = {
>  	.id		= UCLASS_NOP,
>  	.name		= "nop",
> diff --git a/include/dm/uclass.h b/include/dm/uclass.h
> index 7188304..7ac0aaa 100644
> --- a/include/dm/uclass.h
> +++ b/include/dm/uclass.h
> @@ -381,6 +381,18 @@ int uclass_first_device_drvdata(enum uclass_id id, ulong driver_data,
>  int uclass_resolve_seq(struct udevice *dev);
>  
>  /**
> + * uclass_probe_all() - Probe all devices based on an uclass ID
> + *
> + * Every uclass is identified by an ID, a number from 0 to n-1 where n is
> + * the number of uclasses. This function probe all devices asocciated with

nit: probes associated

> + * a uclass by looking its ID.

nit: for its

AFAICT uclass_find_next_device walks the linked-list of devices in a
uclass, and does not care about the ID. So this documentation is
incorrect.

> + *
> + * @id: uclass ID to look up
> + * @return 0 if OK, other -ve on error
> + */
> +int uclass_probe_all(enum uclass_id id);
> +
> +/**
>   * uclass_id_foreach_dev() - Helper function to iteration through devices
>   *
>   * This creates a for() loop which works through the available devices in
>

> -----Original Message-----
> From: Sean Anderson <seanga2@gmail.com>
> Sent: Thursday, November 19, 2020 9:05 AM
> To: Vabhav Sharma (OSS) <vabhav.sharma@oss.nxp.com>;
> sjg@chromium.org; sr@denx.de
> Cc: u-boot@lists.denx.de; Varun Sethi <V.Sethi@nxp.com>;
> andre.przywara@arm.com; Vabhav Sharma <vabhav.sharma@nxp.com>
> Subject: Re: [PATCH v4 1/2] dm: core: add function uclass_probe_all() to
> probe all devices
> 
> On 11/17/20 10:00 AM, Vabhav Sharma wrote:
> > From: Vabhav Sharma <vabhav.sharma@nxp.com>
> >
> > Support a common method to probe all devices associated with uclass.
> >
> > This includes data structures and code for finding the first device
> > and looping for remaining devices associated with uclasses (groups of
> > devices with the same purpose, e.g. all SERIAL ports will be in the same
> uclass).
> >
> > An example is SBSA compliant PL011 UART IP, where firmware does the
> > serial port initialization and prepare uart device to let the kernel
> > use it for sending and reveiving the characters.SERIAL uclass will use
> > this function to initialize PL011 UART ports.
> >
> > The feature is enabled with CONFIG_DM.
> >
> > Signed-off-by: Vabhav Sharma <vabhav.sharma@nxp.com>
> > Reviewed-by: Stefan Roese <sr@denx.de>
> > Reviewed-by: Simon Glass <sjg@chromium.org>
> > --
> >   v4:
> >   Incorporated review comments of Simon
> >   Removed if (dev)..  conditional check
> >
> >   v3:
> >   Incorporated review comments of Stephan,Simon
> >   Related discussion
> > https://patchwork.ozlabs.org/project/uboot/patch/1601400
> > 385-11854-1-git-send-email-vabhav.sharma@oss.nxp.com/
> > ---
> >  drivers/core/uclass.c | 16 ++++++++++++++++
> >  include/dm/uclass.h   | 12 ++++++++++++
> >  2 files changed, 28 insertions(+)
> >
> > diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c index
> > c3f1b73..a1dc8bb 100644
> > --- a/drivers/core/uclass.c
> > +++ b/drivers/core/uclass.c
> > @@ -792,6 +792,22 @@ int uclass_pre_remove_device(struct udevice
> *dev)
> > }  #endif
> >
> > +int uclass_probe_all(enum uclass_id id) {
> > +	struct udevice *dev;
> > +	int ret;
> > +
> > +	ret = uclass_first_device(id, &dev);
> > +	if (ret || !dev)
> > +		return ret;
> > +
> > +	/* Scanning uclass to probe all devices */
> > +	for (; dev; uclass_next_device(&dev))
> 
> You must check the return value of this function.
Error check is done for first device before passing the device to uclass_next_device(),
I think of other implementation is to combine the first device check and iterating through device list of u-class as 
for (ret = uclass_first_device(id, &dev); dev && !ret;  ret = uclass_next_device(&dev))
	;
But iteration is not required if first device is not found and current changes seems to be ok
Please share valuable feedback
> 
> Also, I would suggest using a while loop instead of an empty for loop.
Please elaborate, Found for loop best suitable to use here
> 
> > +		;
> > +
> > +	return 0;
> > +}
> > +
> >  UCLASS_DRIVER(nop) = {
> >  	.id		= UCLASS_NOP,
> >  	.name		= "nop",
> > diff --git a/include/dm/uclass.h b/include/dm/uclass.h index
> > 7188304..7ac0aaa 100644
> > --- a/include/dm/uclass.h
> > +++ b/include/dm/uclass.h
> > @@ -381,6 +381,18 @@ int uclass_first_device_drvdata(enum uclass_id
> > id, ulong driver_data,  int uclass_resolve_seq(struct udevice *dev);
> >
> >  /**
> > + * uclass_probe_all() - Probe all devices based on an uclass ID
> > + *
> > + * Every uclass is identified by an ID, a number from 0 to n-1 where
> > + n is
> > + * the number of uclasses. This function probe all devices asocciated
> > + with
> 
> nit: probes associated
Ok
> 
> > + * a uclass by looking its ID.
> 
> nit: for its
Sure
> 
> AFAICT uclass_find_next_device walks the linked-list of devices in a uclass,
> and does not care about the ID. So this documentation is incorrect.
This documentation is for new function uclass_probe_all() and understand each Uclass is identified by enum ID e.g. UCLASS_SERIAL for serial devices.
According used the statement  "Every uclass is identified by an ID"

Please suggest.
> 
> > + *
> > + * @id: uclass ID to look up
> > + * @return 0 if OK, other -ve on error  */ int uclass_probe_all(enum
> > +uclass_id id);
> > +
> > +/**
> >   * uclass_id_foreach_dev() - Helper function to iteration through devices
> >   *
> >   * This creates a for() loop which works through the available
> > devices in
> >

On 11/23/20 3:06 AM, Vabhav Sharma (OSS) wrote:
> 
> 
>> -----Original Message-----
>> From: Sean Anderson <seanga2@gmail.com>
>> Sent: Thursday, November 19, 2020 9:05 AM
>> To: Vabhav Sharma (OSS) <vabhav.sharma@oss.nxp.com>;
>> sjg@chromium.org; sr@denx.de
>> Cc: u-boot@lists.denx.de; Varun Sethi <V.Sethi@nxp.com>;
>> andre.przywara@arm.com; Vabhav Sharma <vabhav.sharma@nxp.com>
>> Subject: Re: [PATCH v4 1/2] dm: core: add function uclass_probe_all() to
>> probe all devices
>>
>> On 11/17/20 10:00 AM, Vabhav Sharma wrote:
>>> From: Vabhav Sharma <vabhav.sharma@nxp.com>
>>>
>>> Support a common method to probe all devices associated with uclass.
>>>
>>> This includes data structures and code for finding the first device
>>> and looping for remaining devices associated with uclasses (groups of
>>> devices with the same purpose, e.g. all SERIAL ports will be in the same
>> uclass).
>>>
>>> An example is SBSA compliant PL011 UART IP, where firmware does the
>>> serial port initialization and prepare uart device to let the kernel
>>> use it for sending and reveiving the characters.SERIAL uclass will use
>>> this function to initialize PL011 UART ports.
>>>
>>> The feature is enabled with CONFIG_DM.
>>>
>>> Signed-off-by: Vabhav Sharma <vabhav.sharma@nxp.com>
>>> Reviewed-by: Stefan Roese <sr@denx.de>
>>> Reviewed-by: Simon Glass <sjg@chromium.org>
>>> --
>>>    v4:
>>>    Incorporated review comments of Simon
>>>    Removed if (dev)..  conditional check
>>>
>>>    v3:
>>>    Incorporated review comments of Stephan,Simon
>>>    Related discussion
>>> https://patchwork.ozlabs.org/project/uboot/patch/1601400
>>> 385-11854-1-git-send-email-vabhav.sharma@oss.nxp.com/
>>> ---
>>>   drivers/core/uclass.c | 16 ++++++++++++++++
>>>   include/dm/uclass.h   | 12 ++++++++++++
>>>   2 files changed, 28 insertions(+)
>>>
>>> diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c index
>>> c3f1b73..a1dc8bb 100644
>>> --- a/drivers/core/uclass.c
>>> +++ b/drivers/core/uclass.c
>>> @@ -792,6 +792,22 @@ int uclass_pre_remove_device(struct udevice
>> *dev)
>>> }  #endif
>>>
>>> +int uclass_probe_all(enum uclass_id id) {
>>> +	struct udevice *dev;
>>> +	int ret;
>>> +
>>> +	ret = uclass_first_device(id, &dev);
>>> +	if (ret || !dev)
>>> +		return ret;
>>> +
>>> +	/* Scanning uclass to probe all devices */
>>> +	for (; dev; uclass_next_device(&dev))
>>
>> You must check the return value of this function.
> Error check is done for first device before passing the device to uclass_next_device(),
> I think of other implementation is to combine the first device check and iterating through device list of u-class as
> for (ret = uclass_first_device(id, &dev); dev && !ret;  ret = uclass_next_device(&dev))
> 	;
> But iteration is not required if first device is not found and current changes seems to be ok
> Please share valuable feedback


If the second (or any device after the first) fails to init, then the
error will be silently ignored.

>>
>> Also, I would suggest using a while loop instead of an empty for loop.
> Please elaborate, Found for loop best suitable to use here

In terms of original functionality,

while (dev)
	uclass_next_device(&dev)

However, I suggest

while (dev) {
	ret = uclass_next_device(&dev)
	if (ret)
		return ret;
}

So that errors are handled properly.

>>
>>> +		;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>>   UCLASS_DRIVER(nop) = {
>>>   	.id		= UCLASS_NOP,
>>>   	.name		= "nop",
>>> diff --git a/include/dm/uclass.h b/include/dm/uclass.h index
>>> 7188304..7ac0aaa 100644
>>> --- a/include/dm/uclass.h
>>> +++ b/include/dm/uclass.h
>>> @@ -381,6 +381,18 @@ int uclass_first_device_drvdata(enum uclass_id
>>> id, ulong driver_data,  int uclass_resolve_seq(struct udevice *dev);
>>>
>>>   /**
>>> + * uclass_probe_all() - Probe all devices based on an uclass ID
>>> + *
>>> + * Every uclass is identified by an ID, a number from 0 to n-1 where
>>> + n is
>>> + * the number of uclasses. This function probe all devices asocciated
>>> + with
>>
>> nit: probes associated
> Ok
>>
>>> + * a uclass by looking its ID.
>>
>> nit: for its
> Sure
>>
>> AFAICT uclass_find_next_device walks the linked-list of devices in a uclass,
>> and does not care about the ID. So this documentation is incorrect.
> This documentation is for new function uclass_probe_all() and understand each Uclass is identified by enum ID e.g. UCLASS_SERIAL for serial devices.
> According used the statement  "Every uclass is identified by an ID"
> 
> Please suggest.

Ok, this documentation is confusing because the idea of uclasses being
identified by their UCLASS_XXX id is a very common idea in U-Boot
already. On my first reading, I thought you were instead referring to
udevices being identified by id, when instead you were using
udevice_get_next to get the device. I suggest documenting the method
used to initialize device, and refrain from (re)documenting the method
used to identify the uclass. If someone is confused about that, they
need only refer to the definition of enum uclass_id.

>>
>>> + *
>>> + * @id: uclass ID to look up
>>> + * @return 0 if OK, other -ve on error  */ int uclass_probe_all(enum
>>> +uclass_id id);
>>> +
>>> +/**
>>>    * uclass_id_foreach_dev() - Helper function to iteration through devices
>>>    *
>>>    * This creates a for() loop which works through the available
>>> devices in
>>>
>

> -----Original Message-----
> From: Sean Anderson <seanga2@gmail.com>
> Sent: Monday, November 23, 2020 6:54 PM
> To: Vabhav Sharma (OSS) <vabhav.sharma@oss.nxp.com>;
> sjg@chromium.org; sr@denx.de
> Cc: u-boot@lists.denx.de; Varun Sethi <V.Sethi@nxp.com>;
> andre.przywara@arm.com
> Subject: Re: [PATCH v4 1/2] dm: core: add function uclass_probe_all() to
> probe all devices
> 
> On 11/23/20 3:06 AM, Vabhav Sharma (OSS) wrote:
> >
> >
> >> -----Original Message-----
> >> From: Sean Anderson <seanga2@gmail.com>
> >> Sent: Thursday, November 19, 2020 9:05 AM
> >> To: Vabhav Sharma (OSS) <vabhav.sharma@oss.nxp.com>;
> >> sjg@chromium.org; sr@denx.de
> >> Cc: u-boot@lists.denx.de; Varun Sethi <V.Sethi@nxp.com>;
> >> andre.przywara@arm.com; Vabhav Sharma <vabhav.sharma@nxp.com>
> >> Subject: Re: [PATCH v4 1/2] dm: core: add function uclass_probe_all()
> >> to probe all devices
> >>
> >> On 11/17/20 10:00 AM, Vabhav Sharma wrote:
> >>> From: Vabhav Sharma <vabhav.sharma@nxp.com>
> >>>
> >>> Support a common method to probe all devices associated with uclass.
> >>>
> >>> This includes data structures and code for finding the first device
> >>> and looping for remaining devices associated with uclasses (groups
> >>> of devices with the same purpose, e.g. all SERIAL ports will be in
> >>> the same
> >> uclass).
> >>>
> >>> An example is SBSA compliant PL011 UART IP, where firmware does the
> >>> serial port initialization and prepare uart device to let the kernel
> >>> use it for sending and reveiving the characters.SERIAL uclass will
> >>> use this function to initialize PL011 UART ports.
> >>>
> >>> The feature is enabled with CONFIG_DM.
> >>>
> >>> Signed-off-by: Vabhav Sharma <vabhav.sharma@nxp.com>
> >>> Reviewed-by: Stefan Roese <sr@denx.de>
> >>> Reviewed-by: Simon Glass <sjg@chromium.org>
> >>> --
> >>>    v4:
> >>>    Incorporated review comments of Simon
> >>>    Removed if (dev)..  conditional check
> >>>
> >>>    v3:
> >>>    Incorporated review comments of Stephan,Simon
> >>>    Related discussion
> >>> https://patchwork.ozlabs.org/project/uboot/patch/1601400
> >>> 385-11854-1-git-send-email-vabhav.sharma@oss.nxp.com/
> >>> ---
> >>>   drivers/core/uclass.c | 16 ++++++++++++++++
> >>>   include/dm/uclass.h   | 12 ++++++++++++
> >>>   2 files changed, 28 insertions(+)
> >>>
> >>> diff --git a/drivers/core/uclass.c b/drivers/core/uclass.c index
> >>> c3f1b73..a1dc8bb 100644
> >>> --- a/drivers/core/uclass.c
> >>> +++ b/drivers/core/uclass.c
> >>> @@ -792,6 +792,22 @@ int uclass_pre_remove_device(struct udevice
> >> *dev)
> >>> }  #endif
> >>>
> >>> +int uclass_probe_all(enum uclass_id id) {
> >>> +	struct udevice *dev;
> >>> +	int ret;
> >>> +
> >>> +	ret = uclass_first_device(id, &dev);
> >>> +	if (ret || !dev)
> >>> +		return ret;
> >>> +
> >>> +	/* Scanning uclass to probe all devices */
> >>> +	for (; dev; uclass_next_device(&dev))
> >>
> >> You must check the return value of this function.
> > Error check is done for first device before passing the device to
> > uclass_next_device(), I think of other implementation is to combine
> > the first device check and iterating through device list of u-class as for (ret =
> uclass_first_device(id, &dev); dev && !ret;  ret = uclass_next_device(&dev))
> > 	;
> > But iteration is not required if first device is not found and current
> > changes seems to be ok Please share valuable feedback
> 
> 
> If the second (or any device after the first) fails to init, then the error will be
> silently ignored.
I see
> 
> >>
> >> Also, I would suggest using a while loop instead of an empty for loop.
> > Please elaborate, Found for loop best suitable to use here
> 
> In terms of original functionality,
> 
> while (dev)
> 	uclass_next_device(&dev)
> 
> However, I suggest
> 
> while (dev) {
> 	ret = uclass_next_device(&dev)
> 	if (ret)
> 		return ret;
> }
> 
> So that errors are handled properly.
> 
Sure, I will verify the changes to push next version 
> >>
> >>> +		;
> >>> +
> >>> +	return 0;
> >>> +}
> >>> +
> >>>   UCLASS_DRIVER(nop) = {
> >>>   	.id		= UCLASS_NOP,
> >>>   	.name		= "nop",
> >>> diff --git a/include/dm/uclass.h b/include/dm/uclass.h index
> >>> 7188304..7ac0aaa 100644
> >>> --- a/include/dm/uclass.h
> >>> +++ b/include/dm/uclass.h
> >>> @@ -381,6 +381,18 @@ int uclass_first_device_drvdata(enum uclass_id
> >>> id, ulong driver_data,  int uclass_resolve_seq(struct udevice *dev);
> >>>
> >>>   /**
> >>> + * uclass_probe_all() - Probe all devices based on an uclass ID
> >>> + *
> >>> + * Every uclass is identified by an ID, a number from 0 to n-1
> >>> + where n is
> >>> + * the number of uclasses. This function probe all devices
> >>> + asocciated with
> >>
> >> nit: probes associated
> > Ok
> >>
> >>> + * a uclass by looking its ID.
> >>
> >> nit: for its
> > Sure
> >>
> >> AFAICT uclass_find_next_device walks the linked-list of devices in a
> >> uclass, and does not care about the ID. So this documentation is incorrect.
> > This documentation is for new function uclass_probe_all() and understand
> each Uclass is identified by enum ID e.g. UCLASS_SERIAL for serial devices.
> > According used the statement  "Every uclass is identified by an ID"
> >
> > Please suggest.
> 
> Ok, this documentation is confusing because the idea of uclasses being
> identified by their UCLASS_XXX id is a very common idea in U-Boot already.
> On my first reading, I thought you were instead referring to udevices being
> identified by id, when instead you were using udevice_get_next to get the
> device. I suggest documenting the method used to initialize device, and
> refrain from (re)documenting the method used to identify the uclass. If
> someone is confused about that, they need only refer to the definition of
> enum uclass_id.
Thank you, Will rephrase it
> 
> >>
> >>> + *
> >>> + * @id: uclass ID to look up
> >>> + * @return 0 if OK, other -ve on error  */ int
> >>> +uclass_probe_all(enum uclass_id id);
> >>> +
> >>> +/**
> >>>    * uclass_id_foreach_dev() - Helper function to iteration through
> devices
> >>>    *
> >>>    * This creates a for() loop which works through the available
> >>> devices in
> >>>
> >