Re: [PATCH v7 06/10] pwm: dwc: split pci out of core driver

From: Uwe Kleine-König
Date: Wed Jun 14 2023 - 03:04:20 EST

Next message: Marc Kleine-Budde: "Re: [PATCH v8 2/2] can: m_can: Add hrtimer to generate software interrupt"
Previous message: Christoph Hellwig: "Re: [PATCH] btrfs: remove unneeded variable from unpin_extent_cache()"
In reply to: Ben Dooks: "Re: [PATCH v7 06/10] pwm: dwc: split pci out of core driver"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

On Tue, Jun 13, 2023 at 08:22:34PM +0100, Ben Dooks wrote:
> On 16/02/2023 21:30, Uwe Kleine-König wrote:
> > Hello,
> >
> > On Fri, Dec 23, 2022 at 03:38:16PM +0000, Ben Dooks wrote:
> > > Moving towards adding non-pci support for the driver, move the pci
> > > parts out of the core into their own module. This is partly due to
> > > the module_driver() code only being allowed once in a module and also
> > > to avoid a number of #ifdef if we build a single file in a system
> > > without pci support.
> > >
> > > Signed-off-by: Ben Dooks <ben.dooks@xxxxxxxxxx>
> > > ---
> > > v7:
> > > - re-order kconfig to make dwc core be selected by PCI driver
> > > v6:
> > > - put DWC_PERIOD_NS back to avoid bisect issues
> > > v4:
> > > - removed DWC_PERIOD_NS as not needed
> > > ---
> > > drivers/pwm/Kconfig | 17 +++-
> > > drivers/pwm/Makefile | 1 +
> > > drivers/pwm/pwm-dwc-pci.c | 133 ++++++++++++++++++++++++++++++++
> > > drivers/pwm/pwm-dwc.c | 158 +-------------------------------------
> > > drivers/pwm/pwm-dwc.h | 58 ++++++++++++++
> > > 5 files changed, 209 insertions(+), 158 deletions(-)
> > > create mode 100644 drivers/pwm/pwm-dwc-pci.c
> > > create mode 100644 drivers/pwm/pwm-dwc.h
> > >
> > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> > > index 3f3c53af4a56..8c5ef388a981 100644
> > > --- a/drivers/pwm/Kconfig
> > > +++ b/drivers/pwm/Kconfig
> > > @@ -174,16 +174,25 @@ config PWM_CROS_EC
> > > PWM driver for exposing a PWM attached to the ChromeOS Embedded
> > > Controller.
> > > -config PWM_DWC
> > > - tristate "DesignWare PWM Controller"
> > > - depends on PCI || COMPILE_TEST
> >
> > You're loosing COMPILE_TEST here, as it's not present for the new
> > PWM_DWC.
> >
> > > +config PWM_DWC_CORE
> > > + tristate
> > > depends on HAS_IOMEM
> > > help
> > > - PWM driver for Synopsys DWC PWM Controller attached to a PCI bus.
> > > + PWM driver for Synopsys DWC PWM Controller.
> > > To compile this driver as a module, choose M here: the module
> > > will be called pwm-dwc.
> > > +config PWM_DWC
> > > + tristate "DesignWare PWM Controller (PCI bus)"
> > > + depends on HAS_IOMEM && PCI
> > > + select PWM_DWC_CORE
> > > + help
> > > + PWM driver for Synopsys DWC PWM Controller attached to a PCI bus.
> > > +
> > > + To compile this driver as a module, choose M here: the module
> > > + will be called pwm-dwc-pci.
> > > +
> > > config PWM_EP93XX
> > > tristate "Cirrus Logic EP93xx PWM support"
> > > depends on ARCH_EP93XX || COMPILE_TEST
> > > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> > > index 7bf1a29f02b8..a70d36623129 100644
> > > --- a/drivers/pwm/Makefile
> > > +++ b/drivers/pwm/Makefile
> > > @@ -15,6 +15,7 @@ obj-$(CONFIG_PWM_CLPS711X) += pwm-clps711x.o
> > > obj-$(CONFIG_PWM_CRC) += pwm-crc.o
> > > obj-$(CONFIG_PWM_CROS_EC) += pwm-cros-ec.o
> > > obj-$(CONFIG_PWM_DWC) += pwm-dwc.o
> > > +obj-$(CONFIG_PWM_DWC_PCI) += pwm-dwc-pci.o
> > > obj-$(CONFIG_PWM_EP93XX) += pwm-ep93xx.o
> > > obj-$(CONFIG_PWM_FSL_FTM) += pwm-fsl-ftm.o
> > > obj-$(CONFIG_PWM_HIBVT) += pwm-hibvt.o
> > > diff --git a/drivers/pwm/pwm-dwc-pci.c b/drivers/pwm/pwm-dwc-pci.c
> > > new file mode 100644
> > > index 000000000000..2213d0e7f3c8
> > > --- /dev/null
> > > +++ b/drivers/pwm/pwm-dwc-pci.c
> > > @@ -0,0 +1,133 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * DesignWare PWM Controller driver (PCI part)
> > > + *
> > > + * Copyright (C) 2018-2020 Intel Corporation
> > > + *
> > > + * Author: Felipe Balbi (Intel)
> > > + * Author: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
> > > + * Author: Raymond Tan <raymond.tan@xxxxxxxxx>
> > > + *
> > > + * Limitations:
> > > + * - The hardware cannot generate a 0 % or 100 % duty cycle. Both high and low
> > > + * periods are one or more input clock periods long.
> > > + */
> > > +
> > > +#include <linux/bitops.h>
> > > +#include <linux/export.h>
> > > +#include <linux/kernel.h>
> > > +#include <linux/module.h>
> > > +#include <linux/pci.h>
> > > +#include <linux/pm_runtime.h>
> > > +#include <linux/pwm.h>
> > > +
> > > +#include "pwm-dwc.h"
> > > +
> > > +static int dwc_pwm_probe(struct pci_dev *pci, const struct pci_device_id *id)
> > > +{
> > > + struct device *dev = &pci->dev;
> > > + struct dwc_pwm *dwc;
> > > + int ret;
> > > +
> > > + dwc = dwc_pwm_alloc(dev);
> > > + if (!dwc)
> > > + return -ENOMEM;
> > > +
> > > + ret = pcim_enable_device(pci);
> > > + if (ret) {
> > > + dev_err(dev, "Failed to enable device (%pe)\n", ERR_PTR(ret));
> > > + return ret;
> > > + }
> > > +
> > > + pci_set_master(pci);
> > > +
> > > + ret = pcim_iomap_regions(pci, BIT(0), pci_name(pci));
> > > + if (ret) {
> > > + dev_err(dev, "Failed to iomap PCI BAR (%pe)\n", ERR_PTR(ret));
> > > + return ret;
> > > + }
> > > +
> > > + dwc->base = pcim_iomap_table(pci)[0];
> > > + if (!dwc->base) {
> > > + dev_err(dev, "Base address missing\n");
> > > + return -ENOMEM;
> > > + }
> > > +
> > > + ret = devm_pwmchip_add(dev, &dwc->chip);
> > > + if (ret)
> > > + return ret;
> > > +
> > > + pm_runtime_put(dev);
> > > + pm_runtime_allow(dev);
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static void dwc_pwm_remove(struct pci_dev *pci)
> > > +{
> > > + pm_runtime_forbid(&pci->dev);
> > > + pm_runtime_get_noresume(&pci->dev);
> > > +}
> > > +
> > > +#ifdef CONFIG_PM_SLEEP
> > > +static int dwc_pwm_suspend(struct device *dev)
> > > +{
> > > + struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
> > > + struct dwc_pwm *dwc = pci_get_drvdata(pdev);
> > > + int i;
> > > +
> > > + for (i = 0; i < DWC_TIMERS_TOTAL; i++) {
> > > + if (dwc->chip.pwms[i].state.enabled) {
> > > + dev_err(dev, "PWM %u in use by consumer (%s)\n",
> > > + i, dwc->chip.pwms[i].label);
> > > + return -EBUSY;
> > > + }
> > > + dwc->ctx[i].cnt = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(i));
> > > + dwc->ctx[i].cnt2 = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(i));
> > > + dwc->ctx[i].ctrl = dwc_pwm_readl(dwc, DWC_TIM_CTRL(i));
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static int dwc_pwm_resume(struct device *dev)
> > > +{
> > > + struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
> > > + struct dwc_pwm *dwc = pci_get_drvdata(pdev);
> > > + int i;
> > > +
> > > + for (i = 0; i < DWC_TIMERS_TOTAL; i++) {
> > > + dwc_pwm_writel(dwc, dwc->ctx[i].cnt, DWC_TIM_LD_CNT(i));
> > > + dwc_pwm_writel(dwc, dwc->ctx[i].cnt2, DWC_TIM_LD_CNT2(i));
> > > + dwc_pwm_writel(dwc, dwc->ctx[i].ctrl, DWC_TIM_CTRL(i));
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +#endif
> > > +
> > > +static SIMPLE_DEV_PM_OPS(dwc_pwm_pm_ops, dwc_pwm_suspend, dwc_pwm_resume);
> > > +
> > > +static const struct pci_device_id dwc_pwm_id_table[] = {
> > > + { PCI_VDEVICE(INTEL, 0x4bb7) }, /* Elkhart Lake */
> > > + { } /* Terminating Entry */
> > > +};
> > > +MODULE_DEVICE_TABLE(pci, dwc_pwm_id_table);
> > > +
> > > +static struct pci_driver dwc_pwm_driver = {
> > > + .name = "pwm-dwc",
> > > + .probe = dwc_pwm_probe,
> > > + .remove = dwc_pwm_remove,
> > > + .id_table = dwc_pwm_id_table,
> > > + .driver = {
> > > + .pm = &dwc_pwm_pm_ops,
> > > + },
> > > +};
> > > +
> > > +module_pci_driver(dwc_pwm_driver);
> > > +
> > > +MODULE_AUTHOR("Felipe Balbi (Intel)");
> > > +MODULE_AUTHOR("Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>");
> > > +MODULE_AUTHOR("Raymond Tan <raymond.tan@xxxxxxxxx>");
> > > +MODULE_DESCRIPTION("DesignWare PWM Controller");
> > > +MODULE_LICENSE("GPL");
> > > diff --git a/drivers/pwm/pwm-dwc.c b/drivers/pwm/pwm-dwc.c
> > > index 56cde9da2c0e..90a8ae1252a1 100644
> > > --- a/drivers/pwm/pwm-dwc.c
> > > +++ b/drivers/pwm/pwm-dwc.c
> > > @@ -1,16 +1,12 @@
> > > // SPDX-License-Identifier: GPL-2.0
> > > /*
> > > - * DesignWare PWM Controller driver
> > > + * DesignWare PWM Controller driver core
> > > *
> > > * Copyright (C) 2018-2020 Intel Corporation
> > > *
> > > * Author: Felipe Balbi (Intel)
> > > * Author: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
> > > * Author: Raymond Tan <raymond.tan@xxxxxxxxx>
> > > - *
> > > - * Limitations:
> > > - * - The hardware cannot generate a 0 % or 100 % duty cycle. Both high and low
> > > - * periods are one or more input clock periods long.
> > > */
> > > #include <linux/bitops.h>
> > > @@ -21,51 +17,7 @@
> > > #include <linux/pm_runtime.h>
> > > #include <linux/pwm.h>
> > > -#define DWC_TIM_LD_CNT(n) ((n) * 0x14)
> > > -#define DWC_TIM_LD_CNT2(n) (((n) * 4) + 0xb0)
> > > -#define DWC_TIM_CUR_VAL(n) (((n) * 0x14) + 0x04)
> > > -#define DWC_TIM_CTRL(n) (((n) * 0x14) + 0x08)
> > > -#define DWC_TIM_EOI(n) (((n) * 0x14) + 0x0c)
> > > -#define DWC_TIM_INT_STS(n) (((n) * 0x14) + 0x10)
> > > -
> > > -#define DWC_TIMERS_INT_STS 0xa0
> > > -#define DWC_TIMERS_EOI 0xa4
> > > -#define DWC_TIMERS_RAW_INT_STS 0xa8
> > > -#define DWC_TIMERS_COMP_VERSION 0xac
> > > -
> > > -#define DWC_TIMERS_TOTAL 8
> > > -#define DWC_CLK_PERIOD_NS 10
> > > -
> > > -/* Timer Control Register */
> > > -#define DWC_TIM_CTRL_EN BIT(0)
> > > -#define DWC_TIM_CTRL_MODE BIT(1)
> > > -#define DWC_TIM_CTRL_MODE_FREE (0 << 1)
> > > -#define DWC_TIM_CTRL_MODE_USER (1 << 1)
> > > -#define DWC_TIM_CTRL_INT_MASK BIT(2)
> > > -#define DWC_TIM_CTRL_PWM BIT(3)
> > > -
> > > -struct dwc_pwm_ctx {
> > > - u32 cnt;
> > > - u32 cnt2;
> > > - u32 ctrl;
> > > -};
> > > -
> > > -struct dwc_pwm {
> > > - struct pwm_chip chip;
> > > - void __iomem *base;
> > > - struct dwc_pwm_ctx ctx[DWC_TIMERS_TOTAL];
> > > -};
> > > -#define to_dwc_pwm(p) (container_of((p), struct dwc_pwm, chip))
> > > -
> > > -static inline u32 dwc_pwm_readl(struct dwc_pwm *dwc, u32 offset)
> > > -{
> > > - return readl(dwc->base + offset);
> > > -}
> > > -
> > > -static inline void dwc_pwm_writel(struct dwc_pwm *dwc, u32 value, u32 offset)
> > > -{
> > > - writel(value, dwc->base + offset);
> > > -}
> > > +#include "pwm-dwc.h"
> > > static void __dwc_pwm_set_enable(struct dwc_pwm *dwc, int pwm, int enabled)
> > > {
> > > @@ -196,7 +148,7 @@ static const struct pwm_ops dwc_pwm_ops = {
> > > .owner = THIS_MODULE,
> > > };
> > > -static struct dwc_pwm *dwc_pwm_alloc(struct device *dev)
> > > +struct dwc_pwm *dwc_pwm_alloc(struct device *dev)
> > > {
> > > struct dwc_pwm *dwc;
> > > @@ -211,109 +163,7 @@ static struct dwc_pwm *dwc_pwm_alloc(struct device *dev)
> > > dev_set_drvdata(dev, dwc);
> > > return dwc;
> > > }
> > > -
> > > -static int dwc_pwm_probe(struct pci_dev *pci, const struct pci_device_id *id)
> > > -{
> > > - struct device *dev = &pci->dev;
> > > - struct dwc_pwm *dwc;
> > > - int ret;
> > > -
> > > - dwc = dwc_pwm_alloc(dev);
> > > - if (!dwc)
> > > - return -ENOMEM;
> > > -
> > > - ret = pcim_enable_device(pci);
> > > - if (ret) {
> > > - dev_err(dev, "Failed to enable device (%pe)\n", ERR_PTR(ret));
> > > - return ret;
> > > - }
> > > -
> > > - pci_set_master(pci);
> > > -
> > > - ret = pcim_iomap_regions(pci, BIT(0), pci_name(pci));
> > > - if (ret) {
> > > - dev_err(dev, "Failed to iomap PCI BAR (%pe)\n", ERR_PTR(ret));
> > > - return ret;
> > > - }
> > > -
> > > - dwc->base = pcim_iomap_table(pci)[0];
> > > - if (!dwc->base) {
> > > - dev_err(dev, "Base address missing\n");
> > > - return -ENOMEM;
> > > - }
> > > -
> > > - ret = devm_pwmchip_add(dev, &dwc->chip);
> > > - if (ret)
> > > - return ret;
> > > -
> > > - pm_runtime_put(dev);
> > > - pm_runtime_allow(dev);
> > > -
> > > - return 0;
> > > -}
> > > -
> > > -static void dwc_pwm_remove(struct pci_dev *pci)
> > > -{
> > > - pm_runtime_forbid(&pci->dev);
> > > - pm_runtime_get_noresume(&pci->dev);
> > > -}
> > > -
> > > -#ifdef CONFIG_PM_SLEEP
> > > -static int dwc_pwm_suspend(struct device *dev)
> > > -{
> > > - struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
> > > - struct dwc_pwm *dwc = pci_get_drvdata(pdev);
> > > - int i;
> > > -
> > > - for (i = 0; i < DWC_TIMERS_TOTAL; i++) {
> > > - if (dwc->chip.pwms[i].state.enabled) {
> > > - dev_err(dev, "PWM %u in use by consumer (%s)\n",
> > > - i, dwc->chip.pwms[i].label);
> > > - return -EBUSY;
> > > - }
> > > - dwc->ctx[i].cnt = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT(i));
> > > - dwc->ctx[i].cnt2 = dwc_pwm_readl(dwc, DWC_TIM_LD_CNT2(i));
> > > - dwc->ctx[i].ctrl = dwc_pwm_readl(dwc, DWC_TIM_CTRL(i));
> > > - }
> > > -
> > > - return 0;
> > > -}
> > > -
> > > -static int dwc_pwm_resume(struct device *dev)
> > > -{
> > > - struct pci_dev *pdev = container_of(dev, struct pci_dev, dev);
> > > - struct dwc_pwm *dwc = pci_get_drvdata(pdev);
> > > - int i;
> > > -
> > > - for (i = 0; i < DWC_TIMERS_TOTAL; i++) {
> > > - dwc_pwm_writel(dwc, dwc->ctx[i].cnt, DWC_TIM_LD_CNT(i));
> > > - dwc_pwm_writel(dwc, dwc->ctx[i].cnt2, DWC_TIM_LD_CNT2(i));
> > > - dwc_pwm_writel(dwc, dwc->ctx[i].ctrl, DWC_TIM_CTRL(i));
> > > - }
> > > -
> > > - return 0;
> > > -}
> > > -#endif
> > > -
> > > -static SIMPLE_DEV_PM_OPS(dwc_pwm_pm_ops, dwc_pwm_suspend, dwc_pwm_resume);
> > > -
> > > -static const struct pci_device_id dwc_pwm_id_table[] = {
> > > - { PCI_VDEVICE(INTEL, 0x4bb7) }, /* Elkhart Lake */
> > > - { } /* Terminating Entry */
> > > -};
> > > -MODULE_DEVICE_TABLE(pci, dwc_pwm_id_table);
> > > -
> > > -static struct pci_driver dwc_pwm_driver = {
> > > - .name = "pwm-dwc",
> > > - .probe = dwc_pwm_probe,
> > > - .remove = dwc_pwm_remove,
> > > - .id_table = dwc_pwm_id_table,
> > > - .driver = {
> > > - .pm = &dwc_pwm_pm_ops,
> > > - },
> > > -};
> > > -
> > > -module_pci_driver(dwc_pwm_driver);
> > > +EXPORT_SYMBOL_GPL(dwc_pwm_alloc);
> > > MODULE_AUTHOR("Felipe Balbi (Intel)");
> > > MODULE_AUTHOR("Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>");
> > > diff --git a/drivers/pwm/pwm-dwc.h b/drivers/pwm/pwm-dwc.h
> > > new file mode 100644
> > > index 000000000000..68f98eb76152
> > > --- /dev/null
> > > +++ b/drivers/pwm/pwm-dwc.h
> > > @@ -0,0 +1,58 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> > > +/*
> > > + * DesignWare PWM Controller driver
> > > + *
> > > + * Copyright (C) 2018-2020 Intel Corporation
> > > + *
> > > + * Author: Felipe Balbi (Intel)
> > > + * Author: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
> > > + * Author: Raymond Tan <raymond.tan@xxxxxxxxx>
> > > + */
> > > +
> > > +#define DWC_TIM_LD_CNT(n) ((n) * 0x14)
> > > +#define DWC_TIM_LD_CNT2(n) (((n) * 4) + 0xb0)
> > > +#define DWC_TIM_CUR_VAL(n) (((n) * 0x14) + 0x04)
> > > +#define DWC_TIM_CTRL(n) (((n) * 0x14) + 0x08)
> > > +#define DWC_TIM_EOI(n) (((n) * 0x14) + 0x0c)
> > > +#define DWC_TIM_INT_STS(n) (((n) * 0x14) + 0x10)
> > > +
> > > +#define DWC_TIMERS_INT_STS 0xa0
> > > +#define DWC_TIMERS_EOI 0xa4
> > > +#define DWC_TIMERS_RAW_INT_STS 0xa8
> > > +#define DWC_TIMERS_COMP_VERSION 0xac
> > > +
> > > +#define DWC_TIMERS_TOTAL 8
> > > +#define DWC_CLK_PERIOD_NS 10
> > > +
> > > +/* Timer Control Register */
> > > +#define DWC_TIM_CTRL_EN BIT(0)
> > > +#define DWC_TIM_CTRL_MODE BIT(1)
> > > +#define DWC_TIM_CTRL_MODE_FREE (0 << 1)
> > > +#define DWC_TIM_CTRL_MODE_USER (1 << 1)
> > > +#define DWC_TIM_CTRL_INT_MASK BIT(2)
> > > +#define DWC_TIM_CTRL_PWM BIT(3)
> > > +
> > > +struct dwc_pwm_ctx {
> > > + u32 cnt;
> > > + u32 cnt2;
> > > + u32 ctrl;
> > > +};
> > > +
> > > +struct dwc_pwm {
> > > + struct pwm_chip chip;
> > > + void __iomem *base;
> > > + struct dwc_pwm_ctx ctx[DWC_TIMERS_TOTAL];
> > > +};
> > > +#define to_dwc_pwm(p) (container_of((p), struct dwc_pwm, chip))
> > > +
> > > +static inline u32 dwc_pwm_readl(struct dwc_pwm *dwc, u32 offset)
> > > +{
> > > + return readl(dwc->base + offset);
> > > +}
> > > +
> > > +static inline void dwc_pwm_writel(struct dwc_pwm *dwc, u32 value, u32 offset)
> > > +{
> > > + writel(value, dwc->base + offset);
> > > +}
> > > +
> > > +extern struct dwc_pwm *dwc_pwm_alloc(struct device *dev);
> >
> > If you respin this patch for the COMPILE_TEST issue I pointed out above,
> > would you mind using a module namespace?
> >
> > That would work by adding e.g.
> >
> > #define DEFAULT_SYMBOL_NAMESPACE dwc-pwm
> >
> > to drivers/pwm/pwm-dwc.c (before the includes) and
> >
> > MODULE_IMPORT_NS(dwc-pwm)
> >
> > to drivers/pwm/pwm-dwc.h.
> >
> > Best regards
> > Uwe
> >
>
> I tried adding these, but all I get is a bunch of compile errors.

I guess: Add a ; after MODULE_IMPORT_NS(dwc-pwm) fixes that?

To talk code:
https://git.pengutronix.de/cgit/ukl/linux/commit/?h=pwm-dwc-for-bjdooks&id=f3ebe7f1b46f57afee44d42cb8ab3835e8f662c9
works for me.

Best regards
Uwe

--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |

Attachment: signature.asc
Description: PGP signature

Next message: Marc Kleine-Budde: "Re: [PATCH v8 2/2] can: m_can: Add hrtimer to generate software interrupt"
Previous message: Christoph Hellwig: "Re: [PATCH] btrfs: remove unneeded variable from unpin_extent_cache()"
In reply to: Ben Dooks: "Re: [PATCH v7 06/10] pwm: dwc: split pci out of core driver"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]