| Message ID | 20211018204028.2914597-1-u.kleine-koenig@pengutronix.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | fc153aba3ef371d0d76eb88230ed4e0dee5b38f2 |
| Headers | show |
| Series | [v2] usb: max-3421: Use driver data instead of maintaining a list of bound devices | expand |
Looks fine to me. I could only compile-test though since I don't have
this hardware any more.
Ack-by: David Mosberger-Tang <davidm@egauge.net>
Thanks,
--david
On Mon, 2021-10-18 at 22:40 +0200, Uwe Kleine-König wrote:
> Instead of maintaining a single-linked list of devices that must be
> searched linearly in .remove() just use spi_set_drvdata() to remember the
> link between the spi device and the driver struct. Then the global list
> and the next member can be dropped.
>
> This simplifies the driver, reduces the memory footprint and the time to
> search the list. Also it makes obvious that there is always a corresponding
> driver struct for a given device in .remove(), so the error path for
> !max3421_hcd can be dropped, too.
>
> As a side effect this fixes a data inconsistency when .probe() races with
> itself for a second max3421 device in manipulating max3421_hcd_list. A
> similar race is fixed in .remove(), too.
>
> Fixes: 2d53139f3162 ("Add support for using a MAX3421E chip as a host driver.")
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> ---
> Changes since (implicit) v1:
>
> - don't drop "max3421_hcd = hcd_to_max3421(hcd);", noticed by the
> kernel test robot. Greg helped interpreting the kernel test robot's
> finding.
>
> As before, this patch is only build tested.
>
> Best regards
> Uwe
> drivers/usb/host/max3421-hcd.c | 25 +++++--------------------
> 1 file changed, 5 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/usb/host/max3421-hcd.c b/drivers/usb/host/max3421-hcd.c
> index 59cc1bc7f12f..30de85a707fe 100644
> --- a/drivers/usb/host/max3421-hcd.c
> +++ b/drivers/usb/host/max3421-hcd.c
> @@ -125,8 +125,6 @@ struct max3421_hcd {
>
> struct task_struct *spi_thread;
>
> - struct max3421_hcd *next;
> -
> enum max3421_rh_state rh_state;
> /* lower 16 bits contain port status, upper 16 bits the change mask: */
> u32 port_status;
> @@ -174,8 +172,6 @@ struct max3421_ep {
> u8 retransmit; /* packet needs retransmission */
> };
>
> -static struct max3421_hcd *max3421_hcd_list;
> -
> #define MAX3421_FIFO_SIZE 64
>
> #define MAX3421_SPI_DIR_RD 0 /* read register from MAX3421 */
> @@ -1882,9 +1878,8 @@ max3421_probe(struct spi_device *spi)
> }
> set_bit(HCD_FLAG_POLL_RH, &hcd->flags);
> max3421_hcd = hcd_to_max3421(hcd);
> - max3421_hcd->next = max3421_hcd_list;
> - max3421_hcd_list = max3421_hcd;
> INIT_LIST_HEAD(&max3421_hcd->ep_list);
> + spi_set_drvdata(spi, max3421_hcd);
>
> max3421_hcd->tx = kmalloc(sizeof(*max3421_hcd->tx), GFP_KERNEL);
> if (!max3421_hcd->tx)
> @@ -1934,28 +1929,18 @@ max3421_probe(struct spi_device *spi)
> static int
> max3421_remove(struct spi_device *spi)
> {
> - struct max3421_hcd *max3421_hcd = NULL, **prev;
> - struct usb_hcd *hcd = NULL;
> + struct max3421_hcd *max3421_hcd;
> + struct usb_hcd *hcd;
> unsigned long flags;
>
> - for (prev = &max3421_hcd_list; *prev; prev = &(*prev)->next) {
> - max3421_hcd = *prev;
> - hcd = max3421_to_hcd(max3421_hcd);
> - if (hcd->self.controller == &spi->dev)
> - break;
> - }
> - if (!max3421_hcd) {
> - dev_err(&spi->dev, "no MAX3421 HCD found for SPI device %p\n",
> - spi);
> - return -ENODEV;
> - }
> + max3421_hcd = spi_get_drvdata(spi);
> + hcd = max3421_to_hcd(max3421_hcd);
>
> usb_remove_hcd(hcd);
>
> spin_lock_irqsave(&max3421_hcd->lock, flags);
>
> kthread_stop(max3421_hcd->spi_thread);
> - *prev = max3421_hcd->next;
>
> spin_unlock_irqrestore(&max3421_hcd->lock, flags);
>
diff --git a/drivers/usb/host/max3421-hcd.c b/drivers/usb/host/max3421-hcd.c index 59cc1bc7f12f..30de85a707fe 100644 --- a/drivers/usb/host/max3421-hcd.c +++ b/drivers/usb/host/max3421-hcd.c @@ -125,8 +125,6 @@ struct max3421_hcd { struct task_struct *spi_thread; - struct max3421_hcd *next; - enum max3421_rh_state rh_state; /* lower 16 bits contain port status, upper 16 bits the change mask: */ u32 port_status; @@ -174,8 +172,6 @@ struct max3421_ep { u8 retransmit; /* packet needs retransmission */ }; -static struct max3421_hcd *max3421_hcd_list; - #define MAX3421_FIFO_SIZE 64 #define MAX3421_SPI_DIR_RD 0 /* read register from MAX3421 */ @@ -1882,9 +1878,8 @@ max3421_probe(struct spi_device *spi) } set_bit(HCD_FLAG_POLL_RH, &hcd->flags); max3421_hcd = hcd_to_max3421(hcd); - max3421_hcd->next = max3421_hcd_list; - max3421_hcd_list = max3421_hcd; INIT_LIST_HEAD(&max3421_hcd->ep_list); + spi_set_drvdata(spi, max3421_hcd); max3421_hcd->tx = kmalloc(sizeof(*max3421_hcd->tx), GFP_KERNEL); if (!max3421_hcd->tx) @@ -1934,28 +1929,18 @@ max3421_probe(struct spi_device *spi) static int max3421_remove(struct spi_device *spi) { - struct max3421_hcd *max3421_hcd = NULL, **prev; - struct usb_hcd *hcd = NULL; + struct max3421_hcd *max3421_hcd; + struct usb_hcd *hcd; unsigned long flags; - for (prev = &max3421_hcd_list; *prev; prev = &(*prev)->next) { - max3421_hcd = *prev; - hcd = max3421_to_hcd(max3421_hcd); - if (hcd->self.controller == &spi->dev) - break; - } - if (!max3421_hcd) { - dev_err(&spi->dev, "no MAX3421 HCD found for SPI device %p\n", - spi); - return -ENODEV; - } + max3421_hcd = spi_get_drvdata(spi); + hcd = max3421_to_hcd(max3421_hcd); usb_remove_hcd(hcd); spin_lock_irqsave(&max3421_hcd->lock, flags); kthread_stop(max3421_hcd->spi_thread); - *prev = max3421_hcd->next; spin_unlock_irqrestore(&max3421_hcd->lock, flags);
Instead of maintaining a single-linked list of devices that must be searched linearly in .remove() just use spi_set_drvdata() to remember the link between the spi device and the driver struct. Then the global list and the next member can be dropped. This simplifies the driver, reduces the memory footprint and the time to search the list. Also it makes obvious that there is always a corresponding driver struct for a given device in .remove(), so the error path for !max3421_hcd can be dropped, too. As a side effect this fixes a data inconsistency when .probe() races with itself for a second max3421 device in manipulating max3421_hcd_list. A similar race is fixed in .remove(), too. Fixes: 2d53139f3162 ("Add support for using a MAX3421E chip as a host driver.") Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> --- Changes since (implicit) v1: - don't drop "max3421_hcd = hcd_to_max3421(hcd);", noticed by the kernel test robot. Greg helped interpreting the kernel test robot's finding. As before, this patch is only build tested. Best regards Uwe drivers/usb/host/max3421-hcd.c | 25 +++++-------------------- 1 file changed, 5 insertions(+), 20 deletions(-)