From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [IPv6:2401:3900:2:1::2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 21D561A189D for ; Thu, 2 Oct 2014 16:02:38 +1000 (EST) In-Reply-To: <1412073306-13812-16-git-send-email-mikey@neuling.org> To: Michael Neuling , greg@kroah.com, arnd@arndb.de, benh@kernel.crashing.org From: Michael Ellerman Subject: Re: [PATCH v2 15/17] cxl: Userspace header file. Message-Id: <20141002060237.E9963140180@ozlabs.org> Date: Thu, 2 Oct 2014 16:02:37 +1000 (EST) Cc: cbe-oss-dev@lists.ozlabs.org, mikey@neuling.org, "Aneesh Kumar K.V" , imunsie@au.ibm.com, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, jk@ozlabs.org, anton@samba.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, 2014-30-09 at 10:35:04 UTC, Michael Neuling wrote: > From: Ian Munsie > > This defines structs and magic numbers required for userspace to interact with > the kernel cxl driver via /dev/cxl/afu0.0. > > diff --git a/include/uapi/misc/cxl.h b/include/uapi/misc/cxl.h > new file mode 100644 > index 0000000..6a394b5 > --- /dev/null > +++ b/include/uapi/misc/cxl.h > @@ -0,0 +1,88 @@ > +/* > + * Copyright 2014 IBM Corp. > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License > + * as published by the Free Software Foundation; either version > + * 2 of the License, or (at your option) any later version. > + */ > + > +#ifndef _UAPI_ASM_CXL_H > +#define _UAPI_ASM_CXL_H > + > +#include > +#include > + > +/* ioctls */ > +struct cxl_ioctl_start_work { > + __u64 wed; > + __u64 amr; > + __u64 reserved1; > + __u32 reserved2; > + __s16 num_interrupts; /* -1 = use value from afu descriptor */ > + __u16 process_element; /* returned from kernel */ > + __u64 reserved3; > + __u64 reserved4; > + __u64 reserved5; > + __u64 reserved6; Why so many reserved fields? What mechanism is there that will allow you to ever unreserve them? ie. how does a new userspace detect that the kernel it's running on supports new fields? Or conversely how does a new kernel detect that userspace has passed it a meaningful value in one of the previously reserved fields? > +#define CXL_MAGIC 0xCA > +#define CXL_IOCTL_START_WORK _IOWR(CXL_MAGIC, 0x00, struct cxl_ioctl_start_work) What happened to 0x1 ? > +#define CXL_IOCTL_CHECK_ERROR _IO(CXL_MAGIC, 0x02) > + > +/* events from read() */ > + > +enum cxl_event_type { > + CXL_EVENT_READ_FAIL = -1, I don't see this used? > + CXL_EVENT_RESERVED = 0, > + CXL_EVENT_AFU_INTERRUPT = 1, > + CXL_EVENT_DATA_STORAGE = 2, > + CXL_EVENT_AFU_ERROR = 3, > +}; > + > +struct cxl_event_header { > + __u32 type; > + __u16 size; > + __u16 process_element; > + __u64 reserved1; > + __u64 reserved2; > + __u64 reserved3; > +}; Again lots of reserved fields? > +struct cxl_event_afu_interrupt { > + struct cxl_event_header header; > + __u16 irq; /* Raised AFU interrupt number */ > + __u16 reserved1; > + __u32 reserved2; > + __u64 reserved3; > + __u64 reserved4; > + __u64 reserved5; > +}; > + > +struct cxl_event_data_storage { > + struct cxl_event_header header; > + __u64 addr; > + __u64 reserved1; > + __u64 reserved2; > + __u64 reserved3; > +}; > + > +struct cxl_event_afu_error { > + struct cxl_event_header header; > + __u64 err; > + __u64 reserved1; > + __u64 reserved2; > + __u64 reserved3; > +}; > + > +struct cxl_event { > + union { > + struct cxl_event_header header; > + struct cxl_event_afu_interrupt irq; > + struct cxl_event_data_storage fault; > + struct cxl_event_afu_error afu_err; > + }; > +}; Rather than having the header included in every event, would it be clearer if the cxl_event was: struct cxl_event { struct cxl_event_header header; union { struct cxl_event_afu_interrupt irq; struct cxl_event_data_storage fault; struct cxl_event_afu_error afu_err; }; }; cheers