Re: [PATCH v2] driver: core: Allow subsystems to continue deferring probe
On Fri, Jun 14, 2019 at 12:10:10PM +0200, Rafael J. Wysocki wrote:
> On Fri, Jun 14, 2019 at 11:39 AM Thierry Reding
> wrote:
> >
> > On Fri, Jun 14, 2019 at 11:10:58AM +0200, Greg Kroah-Hartman wrote:
> > > On Thu, Jun 13, 2019 at 07:00:11PM +0200, Thierry Reding wrote:
> > > > From: Thierry Reding
> > > >
>
> [cut]
>
> >
> > To avoid further back and forth, what exactly is it that you would have
> > me do? That is, what do you consider to be the correct way to do this?
> >
> > Would you prefer me to add another function with a different name that
> > reimplements the functionality only with the exception? Something along
> > the lines of:
> >
> > int driver_deferred_probe_check_state_continue(struct device *dev)
> > {
> > int ret;
> >
> > ret = driver_deferred_probe_check_state(dev);
> > if (ret == -ENODEV)
> > return -EPROBE_DEFER;
> >
> > return ret;
> > }
> >
> > ? I'd need to split that up some more to avoid the warning that the
> > inner function prints before returning -ENODEV, but that's a minor
> > detail. Would that API be more to your liking?
>
> Well, why don't you do
>
> static int deferred_probe_check_state_internal(struct device *dev)
> {
> if (!initcalls_done)
> return -EPROBE_DEFER;
>
> if (!deferred_probe_timeout) {
> dev_WARN(dev, "deferred probe timeout, ignoring dependency");
> return -ETIMEDOUT;
> }
>
> return 0;
> }
>
> int driver_deferred_probe_check_state(struct device *dev)
> {
> int ret = deferred_probe_check_state_internal(dev);
>
> if (ret)
> return ret;
>
> dev_warn(dev, "ignoring dependency for device, assuming no driver");
> return -ENODEV;
> }
>
> int driver_deferred_probe_check_state_continue(struct device *dev)
> {
> int ret = deferred_probe_check_state_internal(dev);
>
> if (ret)
> return ret;
>
> return -EPROBE_DEFER;
> }
Yes, that's much more sane. Self-decribing apis are the key here, I did
not want a boolean flag, or any other flag, as part of the public api as
they do not describe what the call does at all.
thanks,
greg k-h
Re: [PATCH v2] driver: core: Allow subsystems to continue deferring probe
On Fri, Jun 14, 2019 at 11:39 AM Thierry Reding
wrote:
>
> On Fri, Jun 14, 2019 at 11:10:58AM +0200, Greg Kroah-Hartman wrote:
> > On Thu, Jun 13, 2019 at 07:00:11PM +0200, Thierry Reding wrote:
> > > From: Thierry Reding
> > >
[cut]
>
> To avoid further back and forth, what exactly is it that you would have
> me do? That is, what do you consider to be the correct way to do this?
>
> Would you prefer me to add another function with a different name that
> reimplements the functionality only with the exception? Something along
> the lines of:
>
> int driver_deferred_probe_check_state_continue(struct device *dev)
> {
> int ret;
>
> ret = driver_deferred_probe_check_state(dev);
> if (ret == -ENODEV)
> return -EPROBE_DEFER;
>
> return ret;
> }
>
> ? I'd need to split that up some more to avoid the warning that the
> inner function prints before returning -ENODEV, but that's a minor
> detail. Would that API be more to your liking?
Well, why don't you do
static int deferred_probe_check_state_internal(struct device *dev)
{
if (!initcalls_done)
return -EPROBE_DEFER;
if (!deferred_probe_timeout) {
dev_WARN(dev, "deferred probe timeout, ignoring dependency");
return -ETIMEDOUT;
}
return 0;
}
int driver_deferred_probe_check_state(struct device *dev)
{
int ret = deferred_probe_check_state_internal(dev);
if (ret)
return ret;
dev_warn(dev, "ignoring dependency for device, assuming no driver");
return -ENODEV;
}
int driver_deferred_probe_check_state_continue(struct device *dev)
{
int ret = deferred_probe_check_state_internal(dev);
if (ret)
return ret;
return -EPROBE_DEFER;
}
Re: [PATCH v2] driver: core: Allow subsystems to continue deferring probe
On Fri, Jun 14, 2019 at 11:10:58AM +0200, Greg Kroah-Hartman wrote:
> On Thu, Jun 13, 2019 at 07:00:11PM +0200, Thierry Reding wrote:
> > From: Thierry Reding
> >
> > Some subsystems, such as pinctrl, allow continuing to defer probe
> > indefinitely. This is useful for devices that depend on resources
> > provided by devices that are only probed after the init stage.
> >
> > One example of this can be seen on Tegra, where the DPAUX hardware
> > contains pinmuxing controls for pins that it shares with an I2C
> > controller. The I2C controller is typically used for communication
> > with a monitor over HDMI (DDC). However, other instances of the I2C
> > controller are used to access system critical components, such as a
> > PMIC. The I2C controller driver will therefore usually be a builtin
> > driver, whereas the DPAUX driver is part of the display driver that
> > is loaded from a module to avoid bloating the kernel image with all
> > of the DRM/KMS subsystem.
> >
> > In this particular case the pins used by this I2C/DDC controller
> > become accessible very late in the boot process. However, since the
> > controller is only used in conjunction with display, that's not an
> > issue.
> >
> > Unfortunately the driver core currently outputs a warning message
> > when a device fails to get the pinctrl before the end of the init
> > stage. That can be confusing for the user because it may sound like
> > an unwanted error occurred, whereas it's really an expected and
> > harmless situation.
> >
> > In order to eliminate this warning, this patch allows callers of the
> > driver_deferred_probe_check_state() helper to specify that they want
> > to continue deferring probe, regardless of whether we're past the
> > init stage or not. All of the callers of that function are updated
> > for the new signature, but only the pinctrl subsystem passes a true
> > value in the new persist parameter if appropriate.
> >
> > Signed-off-by: Thierry Reding
> > ---
> > Changes in v2:
> > - pass persist flag via flags parameter to make the function call easier
> > to understand
> >
> > drivers/base/dd.c| 19 ++-
> > drivers/base/power/domain.c | 2 +-
> > drivers/iommu/of_iommu.c | 2 +-
> > drivers/pinctrl/devicetree.c | 9 +
> > include/linux/device.h | 18 +-
> > 5 files changed, 38 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> > index 0df9b4461766..0399a6f6c479 100644
> > --- a/drivers/base/dd.c
> > +++ b/drivers/base/dd.c
> > @@ -238,23 +238,32 @@ __setup("deferred_probe_timeout=",
> > deferred_probe_timeout_setup);
> > /**
> > * driver_deferred_probe_check_state() - Check deferred probe state
> > * @dev: device to check
> > + * @flags: Flags used to control the behavior of this function. Drivers can
> > + * set the DRIVER_DEFER_PROBE_PERSIST flag to indicate that they want to
> > + * keep trying to probe after built-in drivers have had a chance to
> > probe.
> > + * This is useful for built-in drivers that rely on resources provided by
> > + * modular drivers.
> > *
> > * Returns -ENODEV if init is done and all built-in drivers have had a
> > chance
> > - * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
> > - * timeout has expired, or -EPROBE_DEFER if none of those conditions are
> > met.
> > + * to probe (i.e. initcalls are done) and unless the
> > DRIVER_DEFER_PROBE_PERSIST
> > + * flag is set, -ETIMEDOUT if deferred probe debug timeout has expired, or
> > + * -EPROBE_DEFER if none of those conditions are met.
> > *
> > * Drivers or subsystems can opt-in to calling this function instead of
> > directly
> > * returning -EPROBE_DEFER.
> > */
> > -int driver_deferred_probe_check_state(struct device *dev)
> > +int driver_deferred_probe_check_state(struct device *dev, unsigned long
> > flags)
> > {
> > if (initcalls_done) {
> > if (!deferred_probe_timeout) {
> > dev_WARN(dev, "deferred probe timeout, ignoring
> > dependency");
> > return -ETIMEDOUT;
> > }
> > - dev_warn(dev, "ignoring dependency for device, assuming no
> > driver");
> > - return -ENODEV;
> > +
> > + if ((flags & DRIVER_DEFER_PROBE_PERSIST) == 0) {
> > + dev_warn(dev, "ignoring dependency for device, assuming
> > no driver");
> > + return -ENODEV;
> > + }
> > }
> > return -EPROBE_DEFER;
> > }
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index 33c30c1e6a30..6198c6a30fe2 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -2423,7 +2423,7 @@ static int __genpd_dev_pm_attach(struct device *dev,
> > struct device *base_dev,
> > mutex_unlock(_list_lock);
> > dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
> > __func__,
Re: [PATCH v2] driver: core: Allow subsystems to continue deferring probe
On Thu, Jun 13, 2019 at 07:00:11PM +0200, Thierry Reding wrote:
> From: Thierry Reding
>
> Some subsystems, such as pinctrl, allow continuing to defer probe
> indefinitely. This is useful for devices that depend on resources
> provided by devices that are only probed after the init stage.
>
> One example of this can be seen on Tegra, where the DPAUX hardware
> contains pinmuxing controls for pins that it shares with an I2C
> controller. The I2C controller is typically used for communication
> with a monitor over HDMI (DDC). However, other instances of the I2C
> controller are used to access system critical components, such as a
> PMIC. The I2C controller driver will therefore usually be a builtin
> driver, whereas the DPAUX driver is part of the display driver that
> is loaded from a module to avoid bloating the kernel image with all
> of the DRM/KMS subsystem.
>
> In this particular case the pins used by this I2C/DDC controller
> become accessible very late in the boot process. However, since the
> controller is only used in conjunction with display, that's not an
> issue.
>
> Unfortunately the driver core currently outputs a warning message
> when a device fails to get the pinctrl before the end of the init
> stage. That can be confusing for the user because it may sound like
> an unwanted error occurred, whereas it's really an expected and
> harmless situation.
>
> In order to eliminate this warning, this patch allows callers of the
> driver_deferred_probe_check_state() helper to specify that they want
> to continue deferring probe, regardless of whether we're past the
> init stage or not. All of the callers of that function are updated
> for the new signature, but only the pinctrl subsystem passes a true
> value in the new persist parameter if appropriate.
>
> Signed-off-by: Thierry Reding
> ---
> Changes in v2:
> - pass persist flag via flags parameter to make the function call easier
> to understand
>
> drivers/base/dd.c| 19 ++-
> drivers/base/power/domain.c | 2 +-
> drivers/iommu/of_iommu.c | 2 +-
> drivers/pinctrl/devicetree.c | 9 +
> include/linux/device.h | 18 +-
> 5 files changed, 38 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 0df9b4461766..0399a6f6c479 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -238,23 +238,32 @@ __setup("deferred_probe_timeout=",
> deferred_probe_timeout_setup);
> /**
> * driver_deferred_probe_check_state() - Check deferred probe state
> * @dev: device to check
> + * @flags: Flags used to control the behavior of this function. Drivers can
> + * set the DRIVER_DEFER_PROBE_PERSIST flag to indicate that they want to
> + * keep trying to probe after built-in drivers have had a chance to probe.
> + * This is useful for built-in drivers that rely on resources provided by
> + * modular drivers.
> *
> * Returns -ENODEV if init is done and all built-in drivers have had a chance
> - * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
> - * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
> + * to probe (i.e. initcalls are done) and unless the
> DRIVER_DEFER_PROBE_PERSIST
> + * flag is set, -ETIMEDOUT if deferred probe debug timeout has expired, or
> + * -EPROBE_DEFER if none of those conditions are met.
> *
> * Drivers or subsystems can opt-in to calling this function instead of
> directly
> * returning -EPROBE_DEFER.
> */
> -int driver_deferred_probe_check_state(struct device *dev)
> +int driver_deferred_probe_check_state(struct device *dev, unsigned long
> flags)
> {
> if (initcalls_done) {
> if (!deferred_probe_timeout) {
> dev_WARN(dev, "deferred probe timeout, ignoring
> dependency");
> return -ETIMEDOUT;
> }
> - dev_warn(dev, "ignoring dependency for device, assuming no
> driver");
> - return -ENODEV;
> +
> + if ((flags & DRIVER_DEFER_PROBE_PERSIST) == 0) {
> + dev_warn(dev, "ignoring dependency for device, assuming
> no driver");
> + return -ENODEV;
> + }
> }
> return -EPROBE_DEFER;
> }
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index 33c30c1e6a30..6198c6a30fe2 100644
> --- a/drivers/base/power/domain.c
> +++ b/drivers/base/power/domain.c
> @@ -2423,7 +2423,7 @@ static int __genpd_dev_pm_attach(struct device *dev,
> struct device *base_dev,
> mutex_unlock(_list_lock);
> dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
> __func__, PTR_ERR(pd));
> - return driver_deferred_probe_check_state(base_dev);
> + return driver_deferred_probe_check_state(base_dev, 0);
Again, I said no odd flags for functions, how is anyone supposed to know
what "0" means here?
You just
Re: [PATCH v2] driver: core: Allow subsystems to continue deferring probe
On Thu, Jun 13, 2019 at 7:00 PM Thierry Reding wrote:
>
> From: Thierry Reding
>
> Some subsystems, such as pinctrl, allow continuing to defer probe
> indefinitely. This is useful for devices that depend on resources
> provided by devices that are only probed after the init stage.
>
> One example of this can be seen on Tegra, where the DPAUX hardware
> contains pinmuxing controls for pins that it shares with an I2C
> controller. The I2C controller is typically used for communication
> with a monitor over HDMI (DDC). However, other instances of the I2C
> controller are used to access system critical components, such as a
> PMIC. The I2C controller driver will therefore usually be a builtin
> driver, whereas the DPAUX driver is part of the display driver that
> is loaded from a module to avoid bloating the kernel image with all
> of the DRM/KMS subsystem.
>
> In this particular case the pins used by this I2C/DDC controller
> become accessible very late in the boot process. However, since the
> controller is only used in conjunction with display, that's not an
> issue.
>
> Unfortunately the driver core currently outputs a warning message
> when a device fails to get the pinctrl before the end of the init
> stage. That can be confusing for the user because it may sound like
> an unwanted error occurred, whereas it's really an expected and
> harmless situation.
>
> In order to eliminate this warning, this patch allows callers of the
> driver_deferred_probe_check_state() helper to specify that they want
> to continue deferring probe, regardless of whether we're past the
> init stage or not. All of the callers of that function are updated
> for the new signature, but only the pinctrl subsystem passes a true
> value in the new persist parameter if appropriate.
>
> Signed-off-by: Thierry Reding
> ---
> Changes in v2:
> - pass persist flag via flags parameter to make the function call easier
> to understand
>
> drivers/base/dd.c| 19 ++-
> drivers/base/power/domain.c | 2 +-
> drivers/iommu/of_iommu.c | 2 +-
> drivers/pinctrl/devicetree.c | 9 +
> include/linux/device.h | 18 +-
> 5 files changed, 38 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index 0df9b4461766..0399a6f6c479 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -238,23 +238,32 @@ __setup("deferred_probe_timeout=",
> deferred_probe_timeout_setup);
> /**
> * driver_deferred_probe_check_state() - Check deferred probe state
> * @dev: device to check
> + * @flags: Flags used to control the behavior of this function. Drivers can
> + * set the DRIVER_DEFER_PROBE_PERSIST flag to indicate that they want to
What about calling this flag DRIVER_DEFER_PROBE_CONTINUE ?
Also, I would just say
@flags: Flags used to control the behavior of this function.
here and added the description of the flag below.
> + * keep trying to probe after built-in drivers have had a chance to probe.
> + * This is useful for built-in drivers that rely on resources provided by
> + * modular drivers.
> *
> * Returns -ENODEV if init is done and all built-in drivers have had a chance
> - * to probe (i.e. initcalls are done), -ETIMEDOUT if deferred probe debug
> - * timeout has expired, or -EPROBE_DEFER if none of those conditions are met.
> + * to probe (i.e. initcalls are done) and unless the
> DRIVER_DEFER_PROBE_PERSIST
"unless DRIVER_DEFER_PROBE_CONTINUE is set in @flags"
> + * flag is set, -ETIMEDOUT if deferred probe debug timeout has expired, or
> + * -EPROBE_DEFER if none of those conditions are met.
> *
> * Drivers or subsystems can opt-in to calling this function instead of
> directly
> * returning -EPROBE_DEFER.
And here:
"In that case, passing DRIVER_DEFER_PROBE_CONTINUE in @flags indicates
that the caller wants to keep trying to probe after built-in drivers
have had a chance to probe, which is useful for built-in drivers that
rely on resources provided by modular drivers."
> */
> -int driver_deferred_probe_check_state(struct device *dev)
> +int driver_deferred_probe_check_state(struct device *dev, unsigned long
> flags)
> {
> if (initcalls_done) {
> if (!deferred_probe_timeout) {
> dev_WARN(dev, "deferred probe timeout, ignoring
> dependency");
> return -ETIMEDOUT;
> }
> - dev_warn(dev, "ignoring dependency for device, assuming no
> driver");
> - return -ENODEV;
> +
> + if ((flags & DRIVER_DEFER_PROBE_PERSIST) == 0) {
What about
if (!(flags & DRIVER_DEFER_PROBE_PERSIST)) {
> + dev_warn(dev, "ignoring dependency for device,
> assuming no driver");
> + return -ENODEV;
> + }
> }
> return -EPROBE_DEFER;
> }
> diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> index
Re: [PATCH v2] driver: core: Allow subsystems to continue deferring probe
On Thu, Jun 13, 2019 at 11:00 AM Thierry Reding wrote: > > From: Thierry Reding > > Some subsystems, such as pinctrl, allow continuing to defer probe > indefinitely. This is useful for devices that depend on resources > provided by devices that are only probed after the init stage. > > One example of this can be seen on Tegra, where the DPAUX hardware > contains pinmuxing controls for pins that it shares with an I2C > controller. The I2C controller is typically used for communication > with a monitor over HDMI (DDC). However, other instances of the I2C > controller are used to access system critical components, such as a > PMIC. The I2C controller driver will therefore usually be a builtin > driver, whereas the DPAUX driver is part of the display driver that > is loaded from a module to avoid bloating the kernel image with all > of the DRM/KMS subsystem. > > In this particular case the pins used by this I2C/DDC controller > become accessible very late in the boot process. However, since the > controller is only used in conjunction with display, that's not an > issue. > > Unfortunately the driver core currently outputs a warning message > when a device fails to get the pinctrl before the end of the init > stage. That can be confusing for the user because it may sound like > an unwanted error occurred, whereas it's really an expected and > harmless situation. > > In order to eliminate this warning, this patch allows callers of the > driver_deferred_probe_check_state() helper to specify that they want > to continue deferring probe, regardless of whether we're past the > init stage or not. All of the callers of that function are updated > for the new signature, but only the pinctrl subsystem passes a true > value in the new persist parameter if appropriate. > > Signed-off-by: Thierry Reding > --- > Changes in v2: > - pass persist flag via flags parameter to make the function call easier > to understand > > drivers/base/dd.c| 19 ++- > drivers/base/power/domain.c | 2 +- > drivers/iommu/of_iommu.c | 2 +- > drivers/pinctrl/devicetree.c | 9 + > include/linux/device.h | 18 +- > 5 files changed, 38 insertions(+), 12 deletions(-) Acked-by: Rob Herring
