On Mon, May 10, 2021 at 03:12:07PM +0930, Andrew Jeffery wrote:
> Soon it will be possible for one KCS device to have multiple associated
> chardevs exposed to userspace (for IPMI and raw-style access). However,
> don't prevent userspace from:
>
> 1. Opening more than one chardev at a time, or
> 2. Opening the same chardev more than once.
>
> System behaviour is undefined for both classes of multiple access, so
> userspace must manage itself accordingly.
I don't understand why you want to allow this. If the second open won't
work right, then why allow it? Why remove code that causes the second
open to error?
-corey
>
> The implementation delivers IBF and OBF events to the first chardev
> client to associate with the KCS device. An open on a related chardev
> cannot associate its client with the KCS device and so will not
> receive notification of events. However, any fd on any chardev may race
> their accesses to the data and status registers.
>
> Signed-off-by: Andrew Jeffery <andrew@xxxxxxxx>
> ---
> drivers/char/ipmi/kcs_bmc.c | 34 ++++++++++-------------------
> drivers/char/ipmi/kcs_bmc_aspeed.c | 3 +--
> drivers/char/ipmi/kcs_bmc_npcm7xx.c | 3 +--
> 3 files changed, 14 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/char/ipmi/kcs_bmc.c b/drivers/char/ipmi/kcs_bmc.c
> index 7081541bb6ce..ad9ff13ba831 100644
> --- a/drivers/char/ipmi/kcs_bmc.c
> +++ b/drivers/char/ipmi/kcs_bmc.c
> @@ -55,24 +55,12 @@ EXPORT_SYMBOL(kcs_bmc_update_status);
> irqreturn_t kcs_bmc_handle_event(struct kcs_bmc_device *kcs_bmc)
> {
> struct kcs_bmc_client *client;
> - irqreturn_t rc;
> + irqreturn_t rc = IRQ_NONE;
>
> spin_lock(&kcs_bmc->lock);
> client = kcs_bmc->client;
> - if (client) {
> + if (client)
> rc = client->ops->event(client);
> - } else {
> - u8 status;
> -
> - status = kcs_bmc_read_status(kcs_bmc);
> - if (status & KCS_BMC_STR_IBF) {
> - /* Ack the event by reading the data */
> - kcs_bmc_read_data(kcs_bmc);
> - rc = IRQ_HANDLED;
> - } else {
> - rc = IRQ_NONE;
> - }
> - }
> spin_unlock(&kcs_bmc->lock);
>
> return rc;
> @@ -81,26 +69,28 @@ EXPORT_SYMBOL(kcs_bmc_handle_event);
>
> int kcs_bmc_enable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client)
> {
> - int rc;
> -
> spin_lock_irq(&kcs_bmc->lock);
> - if (kcs_bmc->client) {
> - rc = -EBUSY;
> - } else {
> + if (!kcs_bmc->client) {
> + u8 mask = KCS_BMC_EVENT_TYPE_IBF;
> +
> kcs_bmc->client = client;
> - rc = 0;
> + kcs_bmc_update_event_mask(kcs_bmc, mask, mask);
> }
> spin_unlock_irq(&kcs_bmc->lock);
>
> - return rc;
> + return 0;
> }
> EXPORT_SYMBOL(kcs_bmc_enable_device);
>
> void kcs_bmc_disable_device(struct kcs_bmc_device *kcs_bmc, struct kcs_bmc_client *client)
> {
> spin_lock_irq(&kcs_bmc->lock);
> - if (client == kcs_bmc->client)
> + if (client == kcs_bmc->client) {
> + u8 mask = KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE;
> +
> + kcs_bmc_update_event_mask(kcs_bmc, mask, 0);
> kcs_bmc->client = NULL;
> + }
> spin_unlock_irq(&kcs_bmc->lock);
> }
> EXPORT_SYMBOL(kcs_bmc_disable_device);
> diff --git a/drivers/char/ipmi/kcs_bmc_aspeed.c b/drivers/char/ipmi/kcs_bmc_aspeed.c
> index 8b223e58d900..8a0b1e18e945 100644
> --- a/drivers/char/ipmi/kcs_bmc_aspeed.c
> +++ b/drivers/char/ipmi/kcs_bmc_aspeed.c
> @@ -414,8 +414,7 @@ static int aspeed_kcs_probe(struct platform_device *pdev)
>
> platform_set_drvdata(pdev, priv);
>
> - aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE),
> - KCS_BMC_EVENT_TYPE_IBF);
> + aspeed_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
> aspeed_kcs_enable_channel(kcs_bmc, true);
>
> kcs_bmc_add_device(&priv->kcs_bmc);
> diff --git a/drivers/char/ipmi/kcs_bmc_npcm7xx.c b/drivers/char/ipmi/kcs_bmc_npcm7xx.c
> index f8b7162fb830..ab4a8caf1270 100644
> --- a/drivers/char/ipmi/kcs_bmc_npcm7xx.c
> +++ b/drivers/char/ipmi/kcs_bmc_npcm7xx.c
> @@ -202,8 +202,7 @@ static int npcm7xx_kcs_probe(struct platform_device *pdev)
> if (rc)
> return rc;
>
> - npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE),
> - KCS_BMC_EVENT_TYPE_IBF);
> + npcm7xx_kcs_irq_mask_update(kcs_bmc, (KCS_BMC_EVENT_TYPE_IBF | KCS_BMC_EVENT_TYPE_OBE), 0);
> npcm7xx_kcs_enable_channel(kcs_bmc, true);
>
> pr_info("channel=%u idr=0x%x odr=0x%x str=0x%x\n",
> --
> 2.27.0
>
