Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754415AbcKBHpU (ORCPT ); Wed, 2 Nov 2016 03:45:20 -0400 Received: from kvm5.telegraphics.com.au ([98.124.60.144]:46048 "EHLO kvm5.telegraphics.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750935AbcKBHpT (ORCPT ); Wed, 2 Nov 2016 03:45:19 -0400 Date: Wed, 2 Nov 2016 18:45:26 +1100 (AEDT) From: Finn Thain To: Ondrej Zary cc: Christoph Hellwig , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/6] g_NCR5380: Test the IRQ before accepting it In-Reply-To: <1477945112-25659-3-git-send-email-linux@rainbow-software.org> Message-ID: References: <1477945112-25659-1-git-send-email-linux@rainbow-software.org> <1477945112-25659-3-git-send-email-linux@rainbow-software.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2881 Lines: 93 On Mon, 31 Oct 2016, Ondrej Zary wrote: > Trigger an IRQ first with a test IRQ handler to find out if it really > works. Disable the IRQ if not. > > This prevents hang when incorrect IRQ was specified by user. > Once again, how does it cause a hang? If the user specifies an IRQ, we should trust them. If they don't specify an IRQ then probe (as in patch 5/6). > Signed-off-by: Ondrej Zary > --- > drivers/scsi/g_NCR5380.c | 44 +++++++++++++++++++++++++++++++++++++++++--- > 1 file changed, 41 insertions(+), 3 deletions(-) > > diff --git a/drivers/scsi/g_NCR5380.c b/drivers/scsi/g_NCR5380.c > index 09c660b..0d1f6ad 100644 > --- a/drivers/scsi/g_NCR5380.c > +++ b/drivers/scsi/g_NCR5380.c > @@ -115,6 +115,32 @@ static int NCR5380_probe_irq(struct Scsi_Host *instance) > return irq; > } > > +static bool irq_working; > + > +static irqreturn_t test_irq(int irq, void *dev_id) > +{ > + irq_working = true; > + return IRQ_HANDLED; > +} > + > +/* test if the IRQ is working */ > +static int NCR5380_test_irq(struct Scsi_Host *instance, int irq) > +{ > + struct NCR5380_hostdata *hostdata = shost_priv(instance); > + > + irq_working = false; > + if (request_irq(irq, test_irq, 0, "NCR5380-irqtest", NULL)) > + return -EBUSY; > + NCR5380_trigger_irq(instance); > + NCR5380_read(RESET_PARITY_INTERRUPT_REG); > + free_irq(irq, NULL); > + > + if (!irq_working) > + return -EIO; > + > + return 0; > +} > + IMO the extra complexity is not justified by the possibility of machines with misconfigured BIOS or incorrect module parameters. I don't want another irq probing mechanism. We just got rid of one. But I won't mind if the SCSI maintainers who know ISA better than I do would like to review this. > /* > * Configure I/O address of 53C400A or DTC436 by writing magic numbers > * to ports 0x779 and 0x379. > @@ -323,9 +349,21 @@ static int generic_NCR5380_init_one(struct scsi_host_template *tpnt, > /* set IRQ for HP C2502 */ > if (board == BOARD_HP_C2502) > magic_configure(port_idx, instance->irq, magic); > - if (request_irq(instance->irq, generic_NCR5380_intr, > - 0, "NCR5380", instance)) { > - printk(KERN_WARNING "scsi%d : IRQ%d not free, interrupts disabled\n", instance->host_no, instance->irq); > + ret = NCR5380_test_irq(instance, instance->irq); > + if (ret) { > + printk(KERN_WARNING "scsi%d : IRQ%d not %s, interrupts disabled\n", > + instance->host_no, instance->irq, > + (ret == -EBUSY) ? "free" : "working"); > + instance->irq = NO_IRQ; > + } > + } > + > + if (instance->irq != NO_IRQ) { > + if (request_irq(instance->irq, generic_NCR5380_intr, 0, > + "NCR5380", instance)) { > + printk(KERN_WARNING "scsi%d : IRQ%d not free, interrupts disabled\n", > + instance->host_no, > + instance->irq); > instance->irq = NO_IRQ; > } > } > --