From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Mon, 3 Jun 2019 15:40:02 +0200 From: Cornelia Huck Subject: Re: [PATCH v3 2/8] s390/cio: introduce DMA pools to cio Message-ID: <20190603154002.6da0186f.cohuck@redhat.com> In-Reply-To: <20190603144706.2d458ccc.pasic@linux.ibm.com> References: <20190529122657.166148-1-mimu@linux.ibm.com> <20190529122657.166148-3-mimu@linux.ibm.com> <20190603133745.240c00a7.cohuck@redhat.com> <20190603144706.2d458ccc.pasic@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Halil Pasic Cc: Michael Mueller , KVM Mailing List , Linux-S390 Mailing List , Sebastian Ott , Heiko Carstens , virtualization@lists.linux-foundation.org, "Michael S . Tsirkin" , Christoph Hellwig , Thomas Huth , Christian Borntraeger , Viktor Mihajlovski , Vasily Gorbik , Janosch Frank , Claudio Imbrenda , Farhan Ali , Eric Farman , Pierre Morel List-ID: On Mon, 3 Jun 2019 14:47:06 +0200 Halil Pasic wrote: > On Mon, 3 Jun 2019 13:37:45 +0200 > Cornelia Huck wrote: > > > On Wed, 29 May 2019 14:26:51 +0200 > > Michael Mueller wrote: > > > diff --git a/arch/s390/include/asm/cio.h b/arch/s390/include/asm/cio.h > > > index 1727180e8ca1..43c007d2775a 100644 > > > --- a/arch/s390/include/asm/cio.h > > > +++ b/arch/s390/include/asm/cio.h > > > @@ -328,6 +328,17 @@ static inline u8 pathmask_to_pos(u8 mask) > > > void channel_subsystem_reinit(void); > > > extern void css_schedule_reprobe(void); > > > > > > +extern void *cio_dma_zalloc(size_t size); > > > +extern void cio_dma_free(void *cpu_addr, size_t size); > > > +extern struct device *cio_get_dma_css_dev(void); > > > + > > > +struct gen_pool; > > > > That forward declaration is a bit ugly... > > Can you explain to me what is ugly about it so I can avoid similar > mistakes in the future? > > >I guess the alternative was > > include hell? > > > > What do you mean by include hell? > > I decided to use a forward declaration because the guys that include > "cio.h" are not expected to require the interfaces defined in > linux/genalloc.h. My motivation to do it like this was the principle of > encapsulation. My personal rule-of-thumb is to include the header if it is straightforward enough (e.g. if adding a basic header is enough). If you need to include a header together with all of its friends and family, a forward declaration is probably nicer. And of course, sometimes it is simply needed. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [PATCH v3 2/8] s390/cio: introduce DMA pools to cio Date: Mon, 3 Jun 2019 15:40:02 +0200 Message-ID: <20190603154002.6da0186f.cohuck@redhat.com> References: <20190529122657.166148-1-mimu@linux.ibm.com> <20190529122657.166148-3-mimu@linux.ibm.com> <20190603133745.240c00a7.cohuck@redhat.com> <20190603144706.2d458ccc.pasic@linux.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190603144706.2d458ccc.pasic@linux.ibm.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Halil Pasic Cc: Vasily Gorbik , Linux-S390 Mailing List , Thomas Huth , Claudio Imbrenda , KVM Mailing List , Sebastian Ott , "Michael S . Tsirkin" , Pierre Morel , Farhan Ali , Heiko Carstens , Eric Farman , virtualization@lists.linux-foundation.org, Christoph Hellwig , Christian Borntraeger , Michael Mueller , Viktor Mihajlovski , Janosch Frank List-Id: virtualization@lists.linuxfoundation.org On Mon, 3 Jun 2019 14:47:06 +0200 Halil Pasic wrote: > On Mon, 3 Jun 2019 13:37:45 +0200 > Cornelia Huck wrote: > > > On Wed, 29 May 2019 14:26:51 +0200 > > Michael Mueller wrote: > > > diff --git a/arch/s390/include/asm/cio.h b/arch/s390/include/asm/cio.h > > > index 1727180e8ca1..43c007d2775a 100644 > > > --- a/arch/s390/include/asm/cio.h > > > +++ b/arch/s390/include/asm/cio.h > > > @@ -328,6 +328,17 @@ static inline u8 pathmask_to_pos(u8 mask) > > > void channel_subsystem_reinit(void); > > > extern void css_schedule_reprobe(void); > > > > > > +extern void *cio_dma_zalloc(size_t size); > > > +extern void cio_dma_free(void *cpu_addr, size_t size); > > > +extern struct device *cio_get_dma_css_dev(void); > > > + > > > +struct gen_pool; > > > > That forward declaration is a bit ugly... > > Can you explain to me what is ugly about it so I can avoid similar > mistakes in the future? > > >I guess the alternative was > > include hell? > > > > What do you mean by include hell? > > I decided to use a forward declaration because the guys that include > "cio.h" are not expected to require the interfaces defined in > linux/genalloc.h. My motivation to do it like this was the principle of > encapsulation. My personal rule-of-thumb is to include the header if it is straightforward enough (e.g. if adding a basic header is enough). If you need to include a header together with all of its friends and family, a forward declaration is probably nicer. And of course, sometimes it is simply needed.